Tag: physics

Questions Related to physics

Every electric appliance is marked with

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

  1. power

  2. potential difference

  3. charge

  4. resistance

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Correct Option: A,B
Explanation:

Every electric appliance is marked with it's power and potential difference at which it works. This marking is called rating of an electrical appliances.

State SI unit of electric power.

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

  1. Watt

  2. Kilo watt

  3. Joule

  4. Kilowatt hour

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Correct Option: A
Explanation:

SI unit of electric power is Watt
1 Watt = 1  Volt $\times$ 1 ampere.

In a city, electricity costs $0.12 per kilowatt-hour. A bulb of 150-watt operates for 5 hours. Calculate the cost of electricity which is consumed by the bulb.

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  1. $0.009

  2. $0.09

  3. $0.90

  4. $9.00

  5. $90.00

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Correct Option: B
Explanation:

Cost $=(0.150 kWh) (hr)  \left ( 12 \dfrac {cent}{kWh} \right )= 9 cent
=$0.09$

For a domestic $AC$ supply of $220\ V$ at $50$ cycles per second the potential difference between the terminals of a two-pin electric outlet in a room is given by

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

  1. $V(t) = 220\sqrt {2}\cos (100\pi t)$

  2. $V(t) = 220\cos (50t)$

  3. $V(t) = 220\cos (100\pi t)$

  4. $V(t) = 220\sqrt {2}\cos (50 t)$

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Correct Option: A
Explanation:

Rms value of voltage  $V _{rms} =220 $ volts

Peak value of voltage  $V _o = \sqrt{2}V _{rms}$
$\therefore$ $V _{o} = 220\sqrt{2}$volts   
Frequency  $\nu =50$ $Hz$
$\implies$  $w = 2\pi \nu = 2\pi (50)  = 100\pi$
Thus potential difference is given by  $V = V _o \cos wt$
$\therefore$  $V= 220\sqrt{2} \cos (100 \pi t)$

Which instrument is not used to convert electric energy into heat energy?

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  1. Room heater

  2. Electric Iron

  3. Electric Bell

  4. Electric water heater

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Correct Option: C
Explanation:

Electric Bell is not used to convert electric energy into heat energy as there is no  use of heat in functioning of an electric bell.In electric bell electrical energy is used to convert sound energy.First it converts electric energy into mechanical energy and which is used to produce sound energy.

Therefore,C is correct option.

Household electrical appliances are joined using ________ combination of resistors

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

  1. Parallel

  2. Alternating

  3. Continuous

  4. Series

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Correct Option: A
Explanation:

In a house, there are many electrical appliances that have to run independent of each other. If one appliance is turned on or off it should not affect the other appliances. Thus even if a single appliance is taken out of the circuit (turned off / open switched ) the circuit breaks and hence the current cannot flow in the circuit so every thing turns off.

 So even if a single appliance is taken out of the circuit (turned off / open switched ) the circuit breaks and hence the current cannot flow in the circuit .
In parallel, even if an appliance gets damaged or is turned off ,the current always has other independent dedicated parallel paths to other appliances and hence every appliance is still works well. 

Which statement is wrong from the following?

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

  1. The earthing wire is green coloured.

  2. In India, current flowing through wire is AC and its frequency is $50 \,Hz$.

  3. In India, voltage between two wires is $110 \,V$.

  4. T.V., Tublight, bulbs are connected with $5\, A$ line.

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Correct Option: C
Explanation:

In India, current flowing through wire is A.C and its frequency is $50Hz$ and voltage $220V$.But, Option C said voltage between two wires is 110V110V, which is wrong.

Therefore, C is correct option.

Which one of the following is different from the others?

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  1. Joule

  2. Kilowatt hour

  3. Erg

  4. Watt

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Correct Option: D

Which of the following statements is true?

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

  1. In tree type distribution of electric power, fuses are present only on the main board.

  2. In ring type distribution of electric power, there is an individual fuse for each appliance.

  3. Ring type distribution of electric power is advantageous than the tree type distribution.

  4. All the above.

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Correct Option: D
Explanation:

In tree type distribution of electric power, fuses are present only on the distribution board where as in ring type, there is an individual fuse for each appliance. As there is an individual fuse for each appliance in ring type, only faulty appliance will not work and all the other appliances will not be affected. It is easier to install. So, ring type is advantageous than that of tree type. Hence, choice is (4)

Two bulbs of 100 W and 40 W are connected in series. The current through the 100 W bulb is 1A. The current through the 40 W bulb will be

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

  1. $0.4 A$

  2. $0.6A$

  3. $0.8 A$

  4. $1 A$

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Correct Option: D
Explanation:

As the resistances are connected in series , same current will pass through them.