Physics

Current Electricity and Circuits

377 Questions

Current electricity and circuits questions cover resistors, EMF, internal resistance, and power calculations in series and parallel configurations. Solving these builds a strong understanding of electrical principles and circuit analysis. These physics problems are highly relevant for technical and science aptitude tests.

Resistor combinationsPower dissipationEMF and internal resistanceAC circuit analysisOperational amplifiers

Current Electricity and Circuits Questions

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

The speed at which the current travels in a conductor, is nearly

  1. $3 \times 10^0 ms^{-1}$
  2. $3 \times 10^5 ms^{-1}$
  3. $4 \times 10^6 ms^{-1}$
  4. $3 \times 10^8 ms^{-1}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Current travels in a conductor at a speed approximately equal to speed of light i.e. $3\times 10^8$ $ms^{-1}$.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

A flow of $10^{12}$ electrons per minute in a conducting wire constitutes a current of 

  1. $1.6 \times 10^{-7}\, A$
  2. $1.6 \times 10^{-8}\, A$
  3. $2.67 \times 10^{-9}\, A$
  4. `$2.67 \times 10^{-10}\, A$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Current I = q / t. Total charge q = 10^12 * 1.6*10^-19 = 1.6*10^-7 C. Time t = 60 s. I = 1.6*10^-7 / 60 = 2.67*10^-9 A.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

In a conductor, $6.25\, \times\, 10^{16}$ electrons flow from its end A to B in 2 s. Which is the current flowing through conductor? $(e\, =\, 1.6\, \times\, 10^{-19}\, C)$  

  1. $5 mA$ from B to A.
  2. $5 mA$ from A to B.
  3. $10 mA$ from A to B.
  4. $10 mA$ from B to A.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the question, it is given that the charge of an electron is $e=1.6\times { 10 }^{ -19 }\quad C$.

Therefore, the total charge flowing through the wire in 2 seconds will be given as $6.25\times { 10 }^{ 16 }\times 1.6\times { 10 }^{ -19 }\quad C\quad =10\times { 10 }^{ -3 }\quad C$.

The rate of flow of charge is therefore $\dfrac { 10\times { 10 }^{ -3 } \  C }{ 2  \ seconds\quad  } =5\times { 10 }^{ -3 }\quad C/s$.

one C/s = one amp.

Hence, the current flowing through a conductor is $0.0005 A$, that is $5 mA$.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

If the electric potential difference between the two points is $V$ and resistance $R$, then the current between the points will be:

  1. $VR$
  2. $V/R$
  3. $VR^2$
  4. $V/R^2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ohm's law states that voltage drop across conductor is proportional current in it.

$ V \propto I$
$ V= IR$
The proportionality constant is $R$ which known as resistance of conductor
$I= \dfrac{V}{R}$

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

A cell of e.m.f. $\varepsilon$ and internal resistance $r$ is used to send current to an external resistance R. The current drawn from the cell is :

  1. $\displaystyle \frac{\varepsilon}{(R\, +\, r)}$
  2. $\displaystyle \frac{\varepsilon Rr}{R+r}$
  3. $\displaystyle \frac{\varepsilon R}{R+r}$
  4. $\displaystyle \frac{\varepsilon r}{R+r}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Batteries and cells have an  internal resistance (r) which is measured in ohms. When electricity flows around a circuit, the internal resistance of the cell itself resists the flow of current and so thermal (heat) energy is wasted in the cell itself.

$\varepsilon =I(R+r)$

where,

$\varepsilon $ = electromotive force in volts, V

I = current in amperes, A

R = resistance of the load in the circuit in ohms,

r = internal resistance of the cell in ohms.

The above equation can be written as $I=\dfrac { \varepsilon  }{ R+r } $.

Hence, the expression for the current drawn from the cell is $I=\dfrac { \varepsilon  }{ R+r } $.
Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

It is possible to measure the passage of $50$ electrons per second with a certain sensitive device. This corresponds to a current of :

  1. $8 \times 10^{-18} A$
  2. $1.6 \times 10^{-20} A$
  3. $8 \times 10^{-20} A$
  4. $1.6 \times 10^{-19} A$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation


Let number of electrons per second be n.
Given,
$e = 1.6 \times 10^{-19} C$ ,  $n =50 $
The current is defined as rate of flow of charge,
$I = \dfrac{q}{t} $ 
Hence,
$I = n \times e $

Substituting values,
$I = 50 \times 1.6\times 10^{-19} = 8 \times 10^{-18} A $

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

On a bulb is written 220 volt and 60 watt. Find out the resistance of the bulb and the value of the current flowing through it:

  1. $806.66 ohm\ and\ 0.27 ampere$
  2. $500 ohm \ and\ 2 amphere$
  3. $200 ohm \ and\ 4 ampere$
  4. $100 ohm \ and\ 1 ampere$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$R=\dfrac {V^2}{P}=\dfrac {(60^2)}{220}$
$=806.66 \Omega$
$I=\dfrac {P}{V}$
$=\dfrac {6-0}{220}=0.27$

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

The specific resistance of fuse wire is

  1. high

  2. low

  3. zero

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

Answer: B
a fuse wire is a type of high resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. resistivity is directly depend on resistance for a particular conductor , hence high resistance means high resistivity which is called specific resistance.

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

Which modifications are necessary to determine the resistance of solution by the usual method of measurements on Wheatstone's bridge principle?

  1. A.C. should be used

  2. A conductivity cell is used

  3. Galvanometer is replaced by magic eye or headphone arrangement

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All of the following modifications are necessary to determine the resistance of solution by the usual method of measurements on Wheatstone's bridge principle.


(A) A.C. should be used.
(B) A conductivity cell is used.
(C) The galvanometer is replaced by magic eye or headphone arrangement.

If D.C. is used, electrolyte solution will go electrolysis and the change in concentration during the passage of current will not allow reaching the steady value of the null point. In A.C. galvanometer does not work. Also to put the solution at one end in the gap of the meter bridge, a conductivity cell is needed.

Hence, the correct option is $D$

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

The resistance of a hot tungsten filament is about $10$ times the cold resistance. What will be the resistance of $100\ W,\ $$200\ V$ lamp when not in use?

  1. $20\Omega$
  2. $40\Omega$
  3. $200 \Omega$
  4. $400 \Omega$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
When the lamp is in use, it is hot.

Using Joule's Law of heating,
$P = \cfrac{V^2}{R}$
$R= \cfrac{200^2}{100}=400\Omega$ when operating 

It is given resistance of hot lamp is 10 times the cold lamp.
Hence, $R _{cold}=\cfrac{400}{10}=40\Omega$
Multiple choice physics effects of electric current thermal effect of electric current heating effect of electric current electric current and its effects

If current is flowing through a 10 $\Omega$ resistor, then indicate in which case the maximum heat will be generated?

  1. Current of $5\ A$ flows for $2\ \text{minutes}$.
  2. Current of $4\ A$ flows for $3\ \text{minutes}$.
  3. Current of $3\ A$ flows for $6\ \text{minutes}$.
  4. Current of $2\ A$ flows for $5\ \text{minutes}$.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat produced is given by
$Q = I^2 R t$

Option A:
$5\ A$ flows for $2\ \text{minutes}$
$Q = 5^2 \times 10 \times 2 = 500\ J$

Option B:

$4\ A$ flows for $3\ \text{minutes}$

$Q = 4^2 \times 10 \times 3 = 480\ J$


Option C:
$3\ A$ flows for $6\ \text{minutes}$
$Q = 3^2 \times 10 \times 6 = 540\ J$

Option D:
$2\ A$ flows for $5\ \text{minutes}$
 $Q = 2^2 \times 10 \times 5 = 200\ J$


Hence, option C is correct.