Physics

Current Electricity and Circuits

450 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 types of cells electricity physics

Which among the following is a standard cell ?

  1. Daniel cell

  2. Cadmium cell

  3. Leclanche cell

  4. Lead accumulator
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The ideal qualities of standard cells as follows:
(1) The cells must be constructed from high purity materials and be reproducible.
(2) Except when current is flowing there should be no chemical reaction taking place in the cell.
(3) When the cell is thermally cycled it must give the same emf at a given temperature regardless of its thermal history.
(4) When a current is passed through the cell, its emf may change, but it must recover rapdidly and completely on cessation of the current.

(1) to (4) above represent an ideal qualities which only the Weston Standard cell approaches. The Weston Standard cell is constructed with the basic materials- mercury, cadmium, sulfuric acid, and water- are all purified by distillation, starting with the purest materials available. Hence out of given cells cadmium cell is the standard cell.

Multiple choice types of cells electricity physics

Button cell is also called as

  1. lithium cell.

  2. nickel-cadmium cell

  3. dry cell

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

Lithium cell has a negative plate of lithium iron phosphate and a positive plate of carbon. It is also called as button cell.

Multiple choice types of cells electricity physics

The power supplied by a battery (or source) is maximum when the external resistance 'R' is equal to the 

  1. Internal resistance 'r'

  2. Half of the internal resistance 'r'

  3. Two times of initial resistance 'r'

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to the Maximum Power Transfer Theorem, the power delivered to an external load is maximized when the load resistance equals the internal resistance of the source. This is derived by setting the derivative of power with respect to R to zero.

Multiple choice types of cells electricity physics

A cell of emf E is connected across a resistance r . The potential difference terminals of the cell is found to be V . The internal resistance of the cell must be 

  1. $\dfrac { \left( E-V \right) V }{ r } $
  2. $\dfrac { 2\left( E-V \right) V }{ r } $
  3. $\dfrac { \left( E-V \right) r }{ V } $
  4. $\left( E-V \right) r$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The terminal voltage V is given by V = E - Ir, where I = V/r_ext. Substituting I, we get V = E - (V/r_ext) * r_int. Rearranging for r_int gives r_int = (E - V) * r_ext / V. The provided options use 'r' as the external resistance.

Multiple choice types of cells electricity physics

A cell drives a current of 1 A in to load of resistance $4W$. On doubling the load resistance. the current is found to be reduced by $40 \%$. The internal resistance of the cell is

  1. $0.5 W$
  2. $1 W$
  3. $4 W$
  4. $2 W$
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice types of cells electricity physics

Primary cell are connected in parallel to

  1. Increase voltage

  2. Decrease capacity

  3. Decrease internal resistance

  4. Make electric current constant
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Equivalent resistance of parallel combination         $\dfrac{1}{R _{eq}}  = \dfrac{1}{R _1}+\dfrac{1}{R _2} + .......$


$\implies$ Equivalent resistance of the parallel combination is less than the minimum of the individual resistance used.

Hence primary cell are connected in parallel to decrease the internal resistance.

Multiple choice types of cells electricity physics

Which of the following is not the storage cell?

  1. Acid cell

  2. NIFE cell

  3. Edison cell

  4. Dry cell
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Dry cell being primary cell, cannot be recharged.
Acids cell are used as car batteries.
The nickel-iron battery (Ni-Fe battery)( also called Edison Cell)  is a rechargable battery having nickel(III) oxide-hydroxide positive plates and iron negative plates, with an electrolyte of potassium hydroxide. It is a very robust battery which is tolerant of abuse, (overcharge, overdischarge, and short-circuiting) and can have very long life even if so treated.

Multiple choice types of cells electricity physics

In which of the following cells polarisation is the major defect?

  1. Voltaic cell

  2. Daniel cell

  3. Leclanche cell

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

The chemical action that occurs in the cell while the current is flowing causes hydrogen bubbles to form on the surface of the anode. This action is called POLARIZATION. Some hydrogen bubbles rise to the surface of the electrolyte and escape into the air, some remain on the surface of the anode. If enough bubbles remain around the anode, the bubbles form a barrier that increases internal resistance. When the internal resistance of the cell increases, the output current is decreased and the voltage of the cell also decreases.

Voltaic cell has a lot of polarization due to ongoing reactions.Daniell cell is an improvement on the voltaic cell using two electrolytes and solves the problem of polarisation.

Multiple choice evs mud and stones soil types types of soil soil - types, uses and need for conservation

It rc and rs respectively represents cuticular and stomatal resistances, the total resistance (R) could be expressed as.

  1. $R=rc+rs$
  2. $R=r-rs$
  3. $\displaystyle\frac{1}{R}=\frac{1}{rc}+\frac{1}{rs}$
  4. $\displaystyle\frac{r}{R}=\frac{1}{rc}-\frac{1}{rc}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In plant physiology, resistances to water vapor diffusion (like cuticular and stomatal resistance) are arranged in series. Therefore, the total resistance R is the sum of the individual resistances: R = rc + rs.

Multiple choice maths percent and percentage use of percentages converting between fractions or decimals and percentages percentage of a quantity

The possible percentage error in computing the parallel resistance $R$ of three resistances $R _{1},R _{2},R _{3}$ from the formula $\dfrac {1}{R}=\dfrac {1}{R _{1}}+\dfrac {1}{R _{2}}+\dfrac {1}{R _{3}}$, if $R _{1},R _{2},R _{3}$ are each by $1.2\%$

  1. $1.2$
  2. $1.3$
  3. $1.3$
  4. $1.7$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For parallel resistances, if each resistance has the same percentage error, the equivalent resistance inherits that same percentage error. With 1/R = 1/R₁ + 1/R₂ + 1/R₃, taking the differential shows that percentage error propagates directly when all resistances have identical % errors.

Multiple choice power work and power work, energy and power physics energy and its forms

A light bulb has the rating 100 W, 220 V. If the supply voltage is 110 V, then power consumed by the bulb is

  1. 50 W

  2. 75 W

  3. 25 W

  4. 20 W
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$P =\dfrac{ V^2}R$  

If $V = 220$ V we have

$100 W =\dfrac{ 220^2}R$

$R = \dfrac{220^2}{100} Ω = 484 Ω$. This is the resistance of the bulb.

When $V = 110$ V, power consumed $=\dfrac{V^2}R= \dfrac{110^2}{484} = 25$ W.

So, 25 W power is consumed when it is operated on 110 V.


Multiple choice physics electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Thermistor follows which law for small variations ________

  1. Charles law

  2. KVL

  3. KCL

  4. Ohms law
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For small changes in the values of current, voltage across a thermistor increases. It attains a peak value. Then the voltage across the thermistor decreases. As a result Ohms law is followed at small variations of current.

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

A student measures the terminal potential difference (V) of a cell (of emf $\varepsilon$ and internal) resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I, then respectively equal to :



  1. $-\in \;and\;r$
  2. $\in \;and\;-r$
  3. $-r\;and\;\in \;$
  4. $r\;and\;-\in$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$E = V + Ir $
$\Rightarrow V=E-Ir$ 
$Comparing\;with\; y = mx + c$ 
$Slope = - r, intercept = E$




Multiple choice physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

When current flows through a conductor, then the order of drift velocity of electrons will be:-

  1. $10^{10} cms^{-1}$
  2. $10^{-2} cms^{-1}$
  3. $10^{4} cms^{-1}$
  4. $10^{-1} cms^{-1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The drift velocity of electrons in a conductor is of the order of $10^{−4} m/s. It is very small compared to the thermal speed which is of the order of 105 m/s.

The answer is $10^{-2}$

Multiple choice physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

When the current in a wire is 1A, the drift velocity is $1.2\times 10^{-4}ms^{-1}$. The drift velocity when current becomes 5 A is

  1. $1.2\times 10^{-4}ms^{-1}$
  2. $3.6\times 10^{-4}ms^{-1}$
  3. $6\times 10^{-4}ms^{-1}$
  4. $4.8\times 10^{-4}ms^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given
Initial current through the wire is $I = 1A$
Initial drift velocity is, $v _d = 1.2 \times 10^{-4} ms^{-1}$
Increased current is, $I' = 5A$
The current, I through the wire is given by
$I = \mu _e.e.A.v _d$
where, $\mu _e$ is the free electron density, e is the charge on electron, A is the area of cross section of the wire and v_d is the drift velocity of electrons. 
Since,  the free electron density, the charge on electron and the area of cross section of the wire are constant, hence
$I \propto v _d$.................(1)
Now, current through the wire is increased to 5 A, if the new drift velocity of electrons is $v' _d$ then
$I' \propto v' _d$................(2)


From (1) and (2), we can write

$\dfrac{v' _d}{v _d} = \dfrac{I'}{I}$

$v' _d = \dfrac{I'}{I} v _d$

$v' _d = \dfrac{5}{1} 1.2 \times 10^{-4}$ 

$v' _d = 6 \times 10^{-4} ms^{-1}$