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Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

An electric bulb rated 220 V - 100 W will fuse if it consumes 131 W. What voltage fluctuations can it withstand?

  1. up to 230 V

  2. up to 241 V

  3. up to 225 V

  4. up to 252 V
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

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

$R = \dfrac{48400}{100} = 484\ ohm$

Given that it will fuse on use of power of $131W$.
Substituting this:
$131 = \dfrac{V^{2}}{484}$

$V^{2} = 131 \times 484 = 63,404$

$\Rightarrow V = 251.8V$   Which is the highest voltage it can experience without fusing.

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

An 1800 W toaster, a 1.3 kW frying pan are plugged into the same $20 A-120V$ line then

  1. fuse will not blow

  2. fuse will blow

  3. supply will spark

  4. fuse is just saved
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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


$I _{frying pan}=\dfrac{1300}{120}= 10.83 A$

$I _{net}= 25.83 A > 20 A$ 

because applied current is more than possible value of current which is given in ques. Hence fuse will blow

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

A fuse wire of circular cross-section and having diameter of $0.4$ mm, allows $3$A of current to pass through it. But if another fuse wire of same material and circular cross-section and having diameter of $0.6$ mm is taken, then the amount of current passed through the fuse is?

  1. $3$A

  2. $3\times \sqrt{\dfrac{3}{2}}$A

  3. $3\times\left(\dfrac{3}{2}\right)^{3/2}$A

  4. $3\times \left(\dfrac{3}{2}\right)$A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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).

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

what is a fuse ?

  1. Over current protection

  2. low resistance and high melting point wire.

  3. low resistance and low melting point wire.

  4. high resistance and low melting point wire.
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

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.

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

What we used to protect the electric circuits from over loading and short circuit ?

  1. capacitance

  2. inductance

  3. fuse wire

  4. filament wire.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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.

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

Complete the following sentences : 

A fuse is a short piece of wire of high .......... and of material of low ..........

  1. resistance, melting point

  2. meting point, resistance

  3. capacitance, melting point.

  4. conductance, melting point
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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.

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

Complete the following sentences :

A fuse wire is made of an alloy of .......... and ..........

  1. lead, tin

  2. nickel , lead

  3. cadmium, lead

  4. nickel, tin
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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.

Hence correct option is option A.

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

 What is the current through an electrical appliance of rating 5 kW, 200 V and can you use a fuse which is rated 8 A ? 

  1. 25 A, yes

  2. 2.5 A, yes

  3. 25 A, no

  4. 2.5 A, no
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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 current through the appliance is given as $I=P/V.$

That is, $I=\dfrac { P }{ V } =\dfrac { 5000 }{ 200 } =25A$.

The fuse of 8 A cannot be used because the current through the appliance is 
greater the fuse rating. When the 25 A current flows through the fuse it will 
blow off and it will not be able to fulfill it purpose.

Hence, a fuse is rated 8 A cannot be used with this appliance.