Fuse - class-XII

Heat lost per second per unit surface area of fuse wire is
$H = \dfrac{I^2 \rho }{2 \pi ^2 r^3}$

Answer: B
a fuse wire is a type of high resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. resistivity is directly depend on resistance for a particular conductor , hence high resistance means high resistivity which is called specific resistance.

Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing. 
The fuse must always be connected to the mains and it must be of correct current rating. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
Hence, the statement 'the current rating of a fuse is 5 A' means that the fuse should trip when the current through it exceeds 5 amperes. So correct option is B.

In our homes, we receive supply of electric power through a main supply (mains), either supported through overhead electric poles or by underground cables.The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential. The fuse has a high rating of about 50 amperes. Thus it prevents any damage such as fire to the entire electrical wiring entering the house due to short-circuit or overloading.
The two wires then enter the electricity meter which records the electrical power consumed by us in kilowatt-hour (kWh).
Hence, A fuse is connected in series with the live wire.

A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow. The size and construction of the element is (empirically) determined so that the heat produced for a normal current does not cause the element to attain a high temperature. If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit.
The fuse element is made of zinc, copper, silver, aluminum, or alloys of tin and lead to provide stable and predictable characteristics. The fuse ideally would carry its rated current indefinitely, and melt quickly on a small excess. The element must not be damaged by minor harmless surges of current, and must not oxidize or change its behavior after possibly years of service.

The live wires coming out from the output terminals of kWh meter has another fuse in it called the main fuse. 
The fuse is connected in series with the live wire before it enters the household circuit. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential. The fuse has a high rating of about 50 amperes. Thus it prevents any damage such as fire to the entire electrical wiring entering the house due to short-circuit or overloading.Hence correct option is A.

The live wires coming out from the output terminals of kWh meter has another fuse in it called the main fuse. 
The fuse is connected in series with the live wire before it enters the household circuit. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential. The fuse has a high rating of about 50 amperes. Thus it prevents any damage such as fire to the entire electrical wiring entering the house due to short-circuit or overloading.Hence correct option is A.

The fuse consists of a porcelain base on which two metal contacts are fixed. The incoming and outgoing phase wires are connected to these metal contacts. Porcelain made fuse carrier used for holding the fuse element or fuse wire. This porcelain made fuse carrier is inserted to the porcelain base for connecting a load side circuit to source side circuit. The main advantage of this type of fuse is that, the fuse carrier can be removed from the fuse base without any chance of coming in contact with the live part of the circuit.

Fuse wire are used in electric circuits to protect home appliances from damaging by huge amount amount of current. Fuse wire should be such that it melts immediately when strong current flows through the circuit. The same is possible if its melting point is low and resistivity or the resistance is high.

The rating of fuse is ,if the current is greater than the rated current then the fuse blows.
So if the rating is 10A, then it is the maximum current that passes through fuse.
If two such fuses are connected in parallel , the total current divides into two components where each can be maximum of 10 A. The maximum total current can be 20 A.
If they are connected in series,same current flows through each of them. The maximum current allowed would be the minimum rated current among the two fuses.So here the current rating will be 10A.

Answer is D.

When the live wire (high potential) is in contact with the earthed metal case (zero potential) and since there is a potential difference, current flows. As there is little to no resistance in the completed path, the current flow is very large (larger than 4 A melting the fuse). The fuse melts due to high current surge and switches off the circuit.

Answer is D.

The power dissipated is given as P=VI.
In this case, the power of each the bulb is 10 W which uses 220 V supply.
So, the amount of current used is I=P/V = 10/220 = 0.045 A. 
The fuse has a power rating of 5 A. Hence, 5 A / 0.045 A = 111 such bulbs can be connected in parallel with security.
Hence, Mr. Antriksh can use 110 bulbs without any problem. 

Answer is C.

A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow. The size and construction of the element is (empirically) determined so that the heat produced for a normal current does not cause the element to attain a high temperature. If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit and the current stops flowing through it.
Hence, the length of the fuse wire is does not matter.

The material used for a fuse wire must have a low melting point so that it melts as soon as excessive current passes through it and thus it can prevent the appliance from damage.

Answer is A.

Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
In this case, the car headlamp is 48 W and the voltage is 12 V.
That is, P = VI, I = P/V = 48/12 = 4 A.
Hence, the fuse of 5 A should be connected to the circuit.

Answer is B.

Fuse boxes contain safety devices called fuses or circuit breakers - MCB (Miniature Circuit Breaker) which are designed to prevent an excess of electric current entering your house by only allowing a certain maximum current to flow in. When the electrical current is too large, an electromagnet attracts a spring loaded switch which breaks the circuit and cuts the power supply. The switch must be reset before any current can flow again.

Answer is A.

The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse F1. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential.

Its length is immaterial for an electric fuse fuse is used to avoid danger due to high current if high current is passed through the fuse it burns and disconnect the power supply the thickness of fuse determines how much current can be pass hence fuse of any length can be used but it's thickness should be proper

Answer is B.

The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse F1. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential.

The fuse wire is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics. Fuse should be of low resistance and low melting point as per the requirement current rating for overcurrent protection.

A fuse is always connected to the neutral wire.T his statement is false. Fuse is connected to live wire.

Fuse is always connected to live wire. The purpose of a fuse is to protect the wiring and equipment from overloading

Yes,given statement is true, because short-cicuiting is an  excessive current flow in the power source through the short due to which the fuse wire melts and breaks the electric circuit.

Fuses are always connected in series with the components to be protected from overcurrent, so that when the fuse blows (opens) it will open the entire circuit and stop current through the components. A fuse connected in one branch of a parallel circuit, of course, would not affect current through any of the other branches.

Fuses should be connected to the neutral wire.T his statement is false fuses should be connected to live wire.

Fuses used in household generally have a rating of 5A to prevent fuse to melt and prevent circuit to break.

The maximum current which can flow through a fuse without melting it is called its rating.for example a fuse rated at 8A,can stand current upto 8 A. If current higher than 8 A flows through the fuse, it would melt and circuit gets broken the rating of a fuse depends upon the thickness of the fuse wire (because length of the wire is fixed). The thicker fuse has higher rating. So, the thickness of the fuse wire in 8 A circuit is more than that of the fuse wire in 5 A circuit.

A fuse is a piece of thin wire of a material having low melting point, high resistance. It is based in heating effect on current.

Fuse is generally made up of  an alloy of tin and lead. It is used in series with an appliance to prevent it from damage when excessive flows through the appliance. Material to be used in fuse wire must have Low melting point, low boiling point and high electric resistance.

Fuse wire has 

A fuse is always connected in series because 

An MCB functions by interrupting the continuity of electrical flow through the circuit once a fault is detected. In simple terms MCB is a switch which automatically turns off when the current flowing through it passes the maximum allowable limit.

An MCB or miniature circuit breaker is an electromagnetic device that embodies complete enclosure in a molded insulating material.

Nowadays MCB in low voltage electrical network is commonly used instead of fuse. The fuse may not sense the overcurrent but the miniature circuit breaker does it in a more reliable way. MCB is much more sensitive to over current than fuse. Handling a MCB is electrically safer than a fuse.

Fuse is a piece of a wire of material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wire gets heated up and melts.

A fuse is an electrical safety device (a component) that removes electrical current from an electrical circuit when the current in the electrical circuit is too high.

The fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics. The fuse ideally would carry its rated current indefinitely, and melt quickly on a small excess.

A fuse wire must melt and break the circuit when current exceeds a safe limit. To do this effectively, it needs high resistance (to generate heat quickly) and a low melting point (to melt before other components).

A fuse wire has a HIGH resistance & LESS melting point. so that it can protect the electric appliances at home by undergoing melting due to excess heat produced because of high resistance. 

Melting point of a fuse wire is low. So by any chance if high current flows through the circuit, the fuse melts because of heat produced in the circuit beyond a permissible limit. A fuse must have high resistance so as to oppose the current flowing through it beyond a safe limit.

When two identical fuses are joined in parallel, the total current capacity is the sum of the individual ratings because the current splits between them. Thus, 10 A + 10 A = 20 A.

A fuse is a type of low resistance resistor that acts as a device to provide over-current protection, of either the load or source circuit.
Where several fuses are connected in series, it is desirable to blow (clear) only the fuse (or other over-current device) electrically closest to the fault. Hence, when two fuses are in series the current rating is simply the current rating of each fuse i.e. in series, the combination acts as a fuse of rating 10 A
When two fuses are in parallel the current rating is simply twice the current rating of each fuse, hence, in parallel, the combination acts as a fuse of rating 20 A.

The heating effect of a fuse wire is primarily determined by its resistance, which depends on its radius and material. The length is generally considered immaterial in basic fuse physics problems.

We know that: $P = \dfrac{V^{2}}{R}$
Using the fact that the bulb is $220V - 100W$
$ 100 = \dfrac{220^{2}}{R}$

$I _{toaster}=\dfrac{1800}{120}= 15 A,$

The current I that a fuse wire can carry is proportional to the radius raised to the power of 1.5 (or diameter to the power of 1.5). Given d1=0.4 and d2=0.6, the ratio is (0.6/0.4)^(3/2) = (3/2)^(3/2). Thus, I2 = 3 * (3/2)^(3/2).

Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.

A  fuse is the device to protect the electric circuits from over loading and short circuit.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing. 
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps. Hence correct option is C.

A  fuse is the device to protect the electric circuits from over loading and short circuit.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing. 
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
Hence, A fuse is a short piece of wire of high resistance and of material of low melting point.

A  fuse is the device to protect the electric circuits from over loading and short circuit.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing. 
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
Hence, A fuse wire is made of an alloy of lead and tin If the current in a circuit rises too high, the fuse wire melts.

General household wire has a current supply of 5 ampere. Hence fuse also have that. hence The rating of a fuse connected in the general household lighting circuit is $5A$

Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
In this case, let us consider a device of power 5 kW, that is, 5000 W and 200 V.

The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
As we know, the cross-sectional area of the wires will affect the amount of resistance. Wider wires have a greater cross-sectional area. Water will flow through a wider pipe at a higher rate than it will flow through a narrow pipe. This can be attributed to the lower amount of resistance that is present in the wider pipe. In the same manner, the wider the wire, the less resistance that there will be to the flow of electric charge. When all other variables are the same, charge will flow at higher rates that is, more current through wider wires with greater cross-sectional areas than through thinner wires.
Hence, the 20 A wire is the thicker wire as more amount of current flow through it than the 5 A wire.

The electrical resistance of an electrical conductor is the opposition to the passage of an electric current through that conductor. The SI unit of electrical resistance is the ohm $\Omega $.
When the opposition to the passage of an electric current through that conductor is more it is called high resistance and when the opposition to the passage of an electric current through that conductor is less it is called low resistance.
The amount of resistance determines whether the circuit is a good conductor low resistance, or a bad conductor high resistance. 

Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing. 
Hence, the statement is true as the material used for fuse has low melting point.

Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing. 
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
In this case, the electrical appliance is of 1100 W power and 220 V. So the current that passes through the appliance is calculated from P=VI. That is, I=P/V.
So, I = 1100 W/220 V = 5 A.
Hence, the wire B with current rating of 6 A should be used for the fuse.

Switches, fuses and circuit breakers must be placed in the live wire, not in neutral wire. And all the other statements given are correct.

The commonly used fuse wire is made of an alloy of tin and lead.

A fuse is a piece of wire resistance which acts in a way such that if the voltage in a circuit exceeds the rating of the fuse then the fuse wire melts and the circuit becomes an open circuit, thereby breaking the circuit and preventing the components from getting damaged due to short circuit. Now, if two fuses are in series, the melting of a single fuse can break the circuit and so in series the rating will be 10A. However, in parallel, even if one fuse is melted, the other fuse still works and so the net rating will be 20A.

Usually, there are two separate circuits in a house, the lighting circuit with a 5A fuse and the house circuit with a 15A fuse.

• This means much amount of current will be drawn from the socket.
• If we plug in a washing machine,a hair dryer ,a 1 HP mixer grinder then out socket will simply melt.
• So by using multi-plugs adapter current drawn increase result in over heating.

When by short-circuit or any other reason current exceed its nominal value that time fuse breaks the circuit and so cuts off the high voltage from the appliance which prevent it from damage.

In MCB, whenever continuous current flows, the bimetallic strips is heated and deflect by bending. This deflection of bimetallic strips releases the mechanical latch. It causes to open the miniature circuit breakers contact and the MCB turns of thereby stopping he current to flow in the circuit. Hence $A$ is the wrong statement. 

Fuse wire have high value of resistance so when high magnitude of current flows through it then due to melting point of it it melts by excessive heating. Fuse is used to protect the circuit from any accidental heavy flow of current.

The work of fuse wire to protect electric appliances if some particular amount of current that should not be passed through is passed accidentally.

 Electric fuse wire is a wire which allows only upto a limit of current through it , if a particular amount of value of current is exceeded then it melts down.

Fuse is a device used to save the electric current from overheating due to the sudden increase in the current in the circuit.
It protects the device and the user when the electric current is higher than the normal needed by a circuit, it blows up breaking the circuit.
Hence protecting the circuit from an a power overload.

A fuse is a type of low resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. It just controls the amount of current flowing.
It neither increase the resistance of the circuit nor it allows high current. It doesn't allow high current to pass but that doesn't mean, it protect appliances from heating.

A fuse wire may possibly melt when :
(i) the earth wire is broken
(ii) the fuse is fixed along the neutral wire instead of the live wire.
(iii) there is a short circuit in the electrical circuit.

A fuse wire must be made of a material having less specific heat and low melting point. When the current in electric circuit exceeds a safe, limit, the low value of specific heat results in more increase in temperature and the low value of melting point causes it to melt. It thus saves the electrical appliances from getting damaged.

Fuse are used to protect electric appliances at home from large magnitude of current. they are made up of very high resistance. fuse  blows up (Melts) due to overheating when the current through it exceeds the rated current.

When the circuit is switched on, the temperature of the fuse will increase up to a certain value (below the melting point) and then remains constant At this equilibrium stage, the heat lost by the radiation per second balances the heat liberated per second. That is
$(2\pi rI)H=I^2R$
where $H$ is the rate of loss of heat per unit area, $I$ is the current and $R$ the resistance of the fuse wire.
But $\displaystyle R = \frac {\rho l}{\pi r^2}$

$\displaystyle \therefore H(2\pi rl) = \frac {I^2 \rho l}{\pi r^2}$ or $\displaystyle r^3 = \frac {\rho I _2}{2\pi ^{2}H}$

For a given material of the fuse wire, $\rho$ and $H$ are constants.

$r^3 \propto I^2$

If $r _1$ and $r _2$ are the radii of two fuse wires of the same material which blow $u$ at currents $I _1$ and $I _2$,
respectively, then

$\displaystyle \left ( \frac {r _2}{r _1} \right)^3 = \left ( \frac {I _2}{I _1} \right),$ i.e., $\displaystyle r _2 = r _1 \left ( \frac {I _2}{I _1} \right)^{\displaystyle \frac {2}{3}}$

Given: $I _1 = 5A, r _1 = 0.1 mm, I _2 = 40 A$,

$\displaystyle r _2 = 0.1 \left ( \frac {40}{5}\right)^{\displaystyle \frac {2}{3}} = 0.1 (4) = 0.4mm$

Electric fuse work on the principal of heating effect of current . fuse wire is a wire of high resistance and low melting point. when very large current will pass through it, heat will be generated which will melt the fuse wire and break the circuit.By using electric fuses in home we can protect the home appliances from damaging by large amount of current.

Fuse wire are used to save the home appliances from damagaing by large currents. so they are made up of such materials which have high resistance and low melting point so that they can melt down when unexpected amount of current is passed through.for this work either tin metal or tin-lead alloy will be appropriate. 

$I=15 A, V=220 V, t=30 min$
$Energy=P\times t=VIt$
$=220\times 15\times \frac {30}{60}\times 15$
$=3300\times \frac {1}{2}\times 15 W hr$
$=3.3\times kW\times 7.5 hr$
$=24.75 kW hr$
$Cost=24.75\times 2=Rs. 49.50$

For fuse wire expression for heat produced is given by eq. is  $H = \dfrac{I^2 \rho}{2 \pi ^2r^3}$
Hence, it is independent on length of fuse wire. Thus, the parameter irrelevant for an electric fuse wire is its length.