Tag: physics

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Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

The wire having a green plastic covering is a:

  1. Live wire

  2. Neutral wire

  3. Earth wire

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

During wiring in our houses , we use the traditional concept of using red colour wire as live , black as neutral and green for earth.
These colour codes are used to distinguish between live , earth and neutral

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Marking on a bulb is 60 W, 220 V. What does it signify ?

  1. The bulb is connected across 220 volts, 60 joules of energy is released in every second.

  2. The bulb is connected across 220 volts, 60 joules of energy is released in every minute.

  3. 60 A of current will flow in the bulb.

  4. 220 A of current will flow in the bulb.
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

An electric iron uses a power of $1320 W$ when set to higher temperature. If set to lower temperature one third of higher temperature current is used. If iron is connected to a potential of $220 V$, then power used to lower temperature is _____ .

  1. $220 W$

  2. $440 W$

  3. $660 W$

  4. $880 W$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Power, $P = VI$ (power at high temperature) 


$1320 = 220 I$ (current at high temperature)

Current at high temperature, $I _t = 6A $

$I _{LT} = \dfrac{6}{3} = 2A$ (current at low temperature) 

$P _{LT} = 220 \times2 \ W$

$ = 440 \ W$ (power at low temperature)

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

The electrical appliances in a house are connected in :

  1. series

  2. parallel

  3. either in series or parallel

  4. both in series and parallel
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A parallel connection is preferred in a household circuit.
The main advantages of the parallel system are that the supply can be tapped at any convenient point in the house; moreover each appliance is operated by a separate fuse. If the fuse blows off, only that appliance is to be checked. This system involves less wiring and is cheaper to set up.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Units of power and voltage are represented by

  1. W, V

  2. A, V

  3. W, $\Omega$

  4. V, $\Omega$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In our every day lives we use electrical energy to do work for us. This electrical energy is provided either by our power company through the outlets in our wall, or we can buy stored electrical energy in the form of batteries. Different electrical appliances use electrical energy at different rates. Power is the rate at which work is done. The power rating of an appliance tells us the rate at which it uses electrical energy. For example, a 1500 watt hair dryer uses 1500 joules of electrical energy per second.
In any electrical appliance their is a simple relationship between the power output of a component, the potential difference across that component, and the current running through it. This is because charge times potential difference is energy, so (charge per unit time) times (potential difference) gives (energy per unit time).
Thus, we have $P=V I.$
Substituting $V=I R$ from ohm's law, the power relationship can be rewritten as $P={ I }^{ 2 }R$. From this formula, the resistance can be calculated.

hence correct option is A

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Fill the blank.
Voltmeter is always connected in . . . .with the device.

  1. series

  2. parallel

  3. series and parallel both.

  4. the cell.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. A voltmeter is connected in parallel with a device to measure its voltage.
Hence, the statement is false as the voltmeter is connected in parallel to the device in a circuit.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

The melting point of filament of a bulb is 

  1. very low.

  2. very high.

  3. normal.

  4. none of these.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The electric bulb is the glass enclosure around the filament that often contains a vacuum or is filled with a low-pressure noble gas to prevent the filament from burning out due to evaporation at high temperature. The coiled filaments of incandescent lamps are made up of tungsten, a high resistance material that is drawn into a wire .It has both a high melting point (3382 degrees Celsius) and a low pressure which keep it from melting or evaporating too quickly. Supplying electricity through this coiled tungsten wire generates the light. Due to the resistance, it is heated until the wire becomes white-hot. The emission of light by heating the filament wire to white-hot level is known as incandescence. Here, the electrical energy is converted to heat energy by the resistance of the wire.A fused electric bulb has its filament cut, because at higher temperature for a longer period of time, the tungsten filament melts and the flow of electric current stops and the bulb loses its original utility. 
Hence, the statement is true.