Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

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

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.

  1. $0.12$

  2. $0.24$

  3. $0.06$

  4. $0.03$
Reveal answer Fill a bubble to check yourself
B Correct answer
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)

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

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?

  1. $Rs\ 144$

  2. $Rs\ 222$

  3. $Rs\ 662$

  4. $Rs\ 238$
Reveal answer Fill a bubble to check yourself
A Correct answer
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)

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

Laws of heating is given by :

  1. Joule

  2. Ohm

  3. Maxwell

  4. Faraday
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. cooled

  2. heated

  3. maintains its temperature

  4. heated or cooled depending on the atmosphere
Reveal answer Fill a bubble to check yourself
B Correct answer
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

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

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

  1. electrical potential decreases

  2. electrical potential increases

  3. electrical potential remains uncharged

  4. nothing can be said.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electric field lines point from higher to lower potential. Moving in the direction opposite to the lines of force means moving toward higher potential.

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

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

  1. zero

  2. $1Nm^{-1}$

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

  4. $100 \,Vm^{-1}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

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

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

The electric potential while moving along the lines of force

  1. decreases

  2. increases

  3. remains constant

  4. becomes infinite
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Electric field lines are defined as the path along which a positive test charge would move. Since a positive charge moves from higher to lower potential, the potential decreases along the lines of force.