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Current Electricity - ISC Class 12 Physics Questions with Answers, Page 2

103 past-paper questions on Current Electricity from ISC Class 12 Physics papers (2027-2018), newest first, in full. Questions 21-40 are on this page, 20 to a page. Tap "Show answer" under a question to see its answer.

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2026 · 1 mark · MCQOpen: A fish called an electric eel can generate a voltage up to 800V. If it can…

Choose the correct option.

A fish called an electric eel can generate a voltage up to 800V. If it can supply a current of 5mA, the maximum power it can deliver is:
  • (a)4000W
  • (b)400W
  • (c)40W
  • (d)4W
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Answer

AI

Correct option: (d)

Answer: (d) 4W Power is given by $P = VI = 800\text{ V} \times 5 \times 10^{-3}\text{ A} = 4\text{ W}$.
2026 · 3 marks · NumericalOpen: Figure 5 below shows a battery consisting of three cells. Their emfs and…

Solve the following.

Figure 5 below shows a battery consisting of three cells. Their emfs and internal resistances are also shown. Calculate:
Figure for this question
(a)[1.5]
emf of the battery.
(b)[1.5]
internal resistance of the battery.
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Answer (a)

AI
The two cells in the upper branch are connected in series aiding each other: $E_{\text{top}} = E_1 + E_2 = 2\text{ V} + 4\text{ V} = 6\text{ V}$ $r_{\text{top}} = r_1 + r_2 = 1\,\Omega + 3\,\Omega = 4\,\Omega$ The lower branch has emf $E_{\text{bottom}} = 6\text{ V}$ and internal resistance $r_{\text{bottom}} = 12\,\Omega$. The two branches are in parallel with like terminals connected together. The equivalent emf of the battery is: $E = \frac{\frac{E_{\text{top}}}{r_{\text{top}}} + \frac{E_{\text{bottom}}}{r_{\text{bottom}}}}{\frac{1}{r_{\text{top}}} + \frac{1}{r_{\text{bottom}}}} = \frac{\frac{6}{4} + \frac{6}{12}}{\frac{1}{4} + \frac{1}{12}} = 6\text{ V}$

Final answer: 6 V

Answer (b)

AI
The equivalent internal resistance of the two parallel branches is: $\frac{1}{r} = \frac{1}{r_{\text{top}}} + \frac{1}{r_{\text{bottom}}} = \frac{1}{4\,\Omega} + \frac{1}{12\,\Omega} = \frac{3 + 1}{12\,\Omega} = \frac{4}{12\,\Omega} = \frac{1}{3\,\Omega}$ $r = 3\,\Omega$

Final answer: 3 $\Omega$

2025 · 3 marks · NumericalOpen: Harry sets up a circuit as shown in Figure 7 below. He measures potential…

Solve the following.

Harry sets up a circuit as shown in Figure 7 below. He measures potential difference ‘$V$’ across the variable resistor R with an instrument Y. He also measures current ‘$I$’ flowing through R with another instrument X.
(a)[1.5]
Identify the instruments X and Y.
Figure for part (a)
(b)[1.5]
Using the graph of $V$ against $I$ shown below, calculate: (1) emf ($E$) of the cell. (2) Internal resistance ($r$) of the cell.
Figure for part (b)

No answer yet.

2025 · 2 marks · Short answerOpen: Two cells of electromotive forces (e.m.f.s.) approximately 5 V and 10 V are to…

Answer the following.

Two cells of electromotive forces (e.m.f.s.) approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm. The student sets up the circuit as shown in the diagram. However, he is not able to measure the ratio of e.m.f.s correctly. Analyse the circuit shown and spot a minimum of two errors in the circuit. Explain with proper reasoning.

No answer yet.

2025 · 3 marks · Short answerOpen: The graph below shows the variation of current density ( ) with electric field…

Solve the following.

The graph below shows the variation of current density ($J$) with electric field ($E$) applied to two different metallic wires A and B.
Figure for this question
(a)[1.5]
Which one of the wires, A or B, has higher resistivity?
(b)[1.5]
For a certain value of electric field ($E$), in which wire ‘A’ or ‘B’ is drift velocity greater? Give a reason for your answer.

No answer yet.

2025 · 1 mark · MCQOpen: A current I is flowing through a wire of non-uniform cross-section as shown in…

Choose the correct option.

A current I is flowing through a wire of non-uniform cross-section as shown in the figure. Which of the following options gives the correct variation of current ($I$), drift velocity ($v$), and current density ($j$) across the wire?
  • (a)$I_1 > I_2$, $j_2 = j_1$, $v_2 < v_1$
  • (b)$I_1 = I_2$, $j_2 > j_1$, $v_2 > v_1$
  • (c)$I_1 < I_2$, $j_2 < j_1$, $v_2 = v_1$
  • (d)$I_1 = I_2$, $j_2 = j_1$, $v_2 = v_1$

No answer yet.

2025 · 3 marks · NumericalOpen: Study the two circuits shown in Figure 6 below. The cells in the two circuits…

Solve the following.

Study the two circuits shown in Figure 6 below. The cells in the two circuits are identical to each other. The resistance of the load resistor R is the same in both circuits. If the same current flows through the resistor R in both circuits, calculate the internal resistance of each cell in terms of the resistance of resistor R. Show your calculations.
Figure for this question

No answer yet.

2025 · 1 mark · MCQOpen: Sheetal had 6 identical cells, each of electromotive force (emf) 4 V and…

Choose the correct option.

Sheetal had 6 identical cells, each of electromotive force (emf) 4 V and internal resistance 'r'. She connected them to an external resistor 'R' in two different arrangements as shown and measured the current as '$I_1$' and '$I_2$' respectively. If '$I_2$' is found to be greater than '$I_1$', then which relation is true?
  • (a)$R > r$
  • (b)$R = r$
  • (c)$R < r$
  • (d)$R = 6r$

No answer yet.

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