Tag: household circuits

Questions Related to household circuits

Transmission lines transmit a voltage of $V$ volt to our houses from power stations, then the power $P$ supplied by them is proportional to:

power transmission household electricity household circuits electricity and magnetism physics

  1. $\cfrac{1}{V}$

  2. $V$

  3. ${V}^{2}$

  4. $\cfrac{1}{{V}^{2}}$

Show answer
Correct Option: B
Explanation:

Power supplied is equal to to the voltage multiplied by the current flowing through the wire.

  $\therefore$     $P = VI$
$\implies  P  \propto  V$

From a power station, the power is transmitted at a very high voltage because :

power transmission household electricity household circuits electricity and magnetism physics

  1. It is generated only at high voltage

  2. It is cheaper to produce electricity at high voltage

  3. Electricity at high volatge is less dangerous

  4. There is less loss of energy in transmission at high voltage

Show answer
Correct Option: D
Explanation:

When power is transmitted from power station to different different substation then one important factor is kept in mind that power loss in pathway during transmission over large distances should be minimum. 

we know that P = V I 
so for a particular power that is to be transmitted we can choose a combination of voltage and current so that loss is minimum as much possible.
if we do current high and voltage minimum then due to high current , heat loss will be more and power will get lost , hence voltage is kept high and current is kept low as much possible so that current can not produce high vibrations and collisions  in free electrons insides the wire making a lot of loss of power.
so by keeping voltage to high value the loss is minimum as compared to other cases.

The heart does $1.5\ J$ of work in each heart beat. How many times per minute does it beat if its power is $2W$?

power transmission household electricity household circuits electricity and magnetism physics

  1. $20$

  2. $40$

  3. $60$

  4. $80$

Show answer
Correct Option: B

A boy of mass $55\ kg$, runs up a flight of $40$ stairs, its measuring $0.15\ m$ in $15\ s$, the power developed by the boy in kilowatts and Horse power is

power transmission household electricity household circuits electricity and magnetism physics

  1. $220$ and $0.29$

  2. $625$ and $0.83$

  3. $1.15$ and $0.83$

  4. $6.25$ and $0.83$

Show answer
Correct Option: A

Wires used for electric supply go are generally made up of:

physics household circuits precaution with the electrical circuit precautions to be taken while dealing with current devices used to protect from shock of electric current

  1. silver

  2. aluminium

  3. copper

  4. both b and c

Show answer
Correct Option: D
Explanation:

Electric is generated at power station. It is brought to one house by two thick copper wires or aluminium wires fixed once fall electric poles

High tension wires has

physics household circuits precaution with the electrical circuit precautions to be taken while dealing with current devices used to protect from shock of electric current

  1. high resistance.

  2. low resistance.

  3. high young's modulus.

  4. low young's modulus.

Show answer
Correct Option: B
Explanation:

High tension wire is made by twisting together a number of thin wires insulated from each other so as to provide large surface area. It helps to radiate more heat and prevents burning of wire.

A high tension wire has a _____ resistance. Fill in the blank.

physics household circuits precaution with the electrical circuit precautions to be taken while dealing with current devices used to protect from shock of electric current

  1. Low

  2. High

  3. Equal

  4. None

Show answer
Correct Option: A
Explanation:

A high tension wire has a low resistance and large surface area. Instead of taking a single thick wire of low resistance, it is made by twisted together a number of thin wires insulated from each other so as tat it can radiate the head provided.

A bulb of 40W is producing a light of wavelength 620 nm with 80% of eficiency then no of photons emitted by the bulb in 20 sec are 

physics household circuits precaution with the electrical circuit precautions to be taken while dealing with current devices used to protect from shock of electric current

  1. $2 \times (10) ^ {18}$

  2. $10 \times (10) ^ {18}$

  3. $10 \times (10) ^ {21}$

  4. $2 \times (10) ^ {20}$

Show answer
Correct Option: D
Explanation:

Energy of photon emitted by a bulb,

$E=\dfrac{80}{100}\times 40\times 20=640$
Wavelength of light, $\lambda=620nm$
Energy of photons $E'=\dfrac{hc}{\lambda}$
$=3.2\times 10^{-19}J$
$\therefore$ No of photons emitted , $n=\dfrac E{E'}$
$=\dfrac{640}{32\times 10^{-19}}$
$=2\times 10^{20}$