Tag: physics

Questions Related to physics

An electric bulb is connected to a $20$ V battery of negligible internal resistance. The resistance offered by the bulb is $5$ $\Omega$. The electrical energy consumed by the bulb in $3$ hours is _____ kWh.

physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

  1. $0.12$

  2. $0.24$

  3. $0.06$

  4. $0.03$

Show answer
Correct Option: B
Explanation:

Power consumed by bulb is $P=\dfrac{V^2}{R}$


Energy$=E=Pt=\dfrac{V^2}{R}t=\dfrac{20^2}{5}W\times 3h$

$\implies E=240Wh=0.24kWh$

Answer-(B)

What should be the bill for the month of April for a heater of resistance 60.5 $\Omega$ connected 220 V mains, The cost of energy is Rs 2 per kWh and the heater is used for 3 hours daily?

physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

  1. $Rs\ 144$

  2. $Rs\ 222$

  3. $Rs\ 662$

  4. $Rs\ 238$

Show answer
Correct Option: A
Explanation:

Power of heater $=P=\dfrac{V^2}{R}$


Energy used in one month$=E=Pt=\dfrac{V^2}{R}\times 3\times 30$

$\implies E=\dfrac{220\times 220}{60.5}\times 90Wh=\dfrac{484\times 9}{60.5}kWh=72kWh$

Hence cost$=72\times 2=Rs144$

Answer-(A)

Laws of heating is given by :

physics electric current and circuit thermal effect of electric current heating effect of electric current electric current and its effects

  1. Joule

  2. Ohm

  3. Maxwell

  4. Faraday

Show answer
Correct Option: A
Explanation:

Answer is A.

The heat which is produced due to the flow of  current   within an electric wire, is expressed in Joules.
James Prescott Joule was an English physicist who studied the nature of heat and established its relationship to mechanical work. He therefore laid the foundation for the theory of conservation of energy, which later influenced the First Law of Thermodynamics. He also formulated the Joules laws which deal with the transfer of energy.

An electric fan is switched on in a closed room. The air in the room is 

physics electric current and circuit thermal effect of electric current heating effect of electric current electric current and its effects

  1. cooled

  2. heated

  3. maintains its temperature

  4. heated or cooled depending on the atmosphere

Show answer
Correct Option: B
Explanation:

If an electric fan is switched on in a closed room, the air will be heated because due to motion of the fan, the speed of air molecules will increase. In fact, we feel cold due to evaporation of our sweat

Law of heating was given by

physics electric current and circuit thermal effect of electric current heating effect of electric current electric current and its effects

  1. Joule

  2. Ohm

  3. Maxwell

  4. Faraday

Show answer
Correct Option: A
Explanation:

Laws of heating were given by Joule.

Heat produced in the resistor: $H = I^2Rt$

According to Joule's Law, Which of the quantities do not affect heat produced in a resistor?

physics electric current and circuit thermal effect of electric current heating effect of electric current electric current and its effects

  1. Current

  2. Resistance

  3. Resistivity

  4. Temperature

Show answer
Correct Option: D
Explanation:

By Joule's Law, heat produced

$Q = I^2Rt$
Also, $R = \rho l /A$
Hence, no role of temperature

A/C to Joule's law

physics electric current and circuit thermal effect of electric current heating effect of electric current electric current and its effects

  1. W=JQ

  2. W=Ft

  3. W=It

  4. W=IR

Show answer
Correct Option: A
Explanation:

According to Joule's law,       $W = JQ$

where, $W$ is work done,
             $J$ is Mechanical equivalent of work
            $Q$ is the heat produced

If we move in a direction opposite to the electric lines of force:

physics coulomb's law field strength and potential gradient electric field as gradient of potential relation between electric field and electric potential

  1. electrical potential decreases

  2. electrical potential increases

  3. electrical potential remains uncharged

  4. nothing can be said.

Show answer
Correct Option: B

A uniform wire $10 \,cm$ long is carrying a steady current. The potential drop across it is $10V$. The electric field inside it is _____

physics coulomb's law field strength and potential gradient electric field as gradient of potential relation between electric field and electric potential

  1. zero

  2. $1Nm^{-1}$

  3. $10 \,Vm^{-1}$

  4. $100 \,Vm^{-1}$

Show answer
Correct Option: D
Explanation:

$E = \dfrac{V}{r} = \dfrac{10V}{10 \times 10^{-2}m} = \dfrac{10 \times 100}{10} = 100 \dfrac{v}{m}$

The electric potential while moving along the lines of force

physics coulomb's law field strength and potential gradient electric field as gradient of potential relation between electric field and electric potential

  1. decreases

  2. increases

  3. remains constant

  4. becomes infinite

Show answer
Correct Option: A