Answer the following.
In case of metals, what is the relation between current density ($J$), electrical conductivity ($\sigma$) and electric field intensity ($E$)?
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Current Electricity - ISC Class 12 Physics Questions with Answers, Page 4
103 past-paper questions on Current Electricity from ISC Class 12 Physics papers (2027-2018), newest first, in full. Questions 61-80 are on this page, 20 to a page. Tap "Show answer" under a question to see its answer.
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Solve the following.
In a meter bridge circuit, resistance in the left gap is $4\,\Omega$ and an unknown resistance $R$ is in the right-hand gap as shown in Figure 2 below. The null point is found to be $40\text{ cm}$ from the left end of the wire.
(a)[1.5]
Calculate the value of the unknown resistance $R$.
(b)[1.5]
What change will you make in $R$ to bring the null point to the midpoint of the wire AB?
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Answer the following.
State any one use of a potentiometer.
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Choose the correct option.
An electric current ($I$) flowing through a metallic wire is gradually increased. The graph of heating power ($P$) developed in it versus the current ($I$) is:
- (a)(a)
- (b)(b)
- (c)(c)
- (d)(d)
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Answer the following.
Name the conservation principle implied in Kirchhoff’s Junction law for electric circuits.
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Answer the following.
Write balancing condition of a Wheatstone bridge.
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Solve the following.
A circuit is used to determine the internal resistance and the emf of a cell. It consists of the cell, a variable resistor, an ideal ammeter A and an ideal voltmeter V. Figure 3 shows part of the circuit with the ammeter and voltmeter missing.
The variable resistor is set to be $1\cdot5\,\Omega$. When the cell converts $7\cdot2\text{ mJ}$ of energy, $5\cdot8\text{ mC}$ of charge moves completely around the circuit. The potential difference across the variable resistor is $0\cdot55\text{ V}$.
(a)[1.5]
Redraw the diagram showing the positions of the ammeter and the voltmeter.
(b)[1.5]
Calculate the emf of the cell.
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Choose the correct option.
If $R_1$ and $R_2$ are filament resistances of a $100\text{ W}$ bulb and a $50\text{ W}$ bulb respectively, designed to operate on the same voltage, then:
- (a)$R_1 = R_2$
- (b)$R_1 = 4R_2$
- (c)$R_2 = 4R_1$
- (d)$R_2 = 2R_1$
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Solve the following.
Eight identical cells, each of emf $2\text{ V}$ and internal resistance $3\,\Omega$, are connected in series to form a row. Six such rows are connected in parallel to form a battery. This battery is now connected to an external resistor R of resistance $6\,\Omega$. Calculate:
(a)[1.0]
emf of the battery.
(b)[1.0]
internal resistance of the battery.
(c)[1.0]
current flowing through R.
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Choose the correct option.
The circuit shown in figure 9 below is used to compare the e.m.f. of two cells $E_1$ and $E_2$ where $E_2 > E_1$. The null point is at C when the galvanometer is connected to $E_1$. When the galvanometer is connected to $E_2$, the null point will be:
- (a)To the left of C
- (b)To the right of C
- (c)At C itself
- (d)Nowhere on AB
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The current in the circuit shown in figure 7 below, will be:
- (a)$1/45\text{ A}$
- (b)$1/15\text{ A}$
- (c)$1/10\text{ A}$
- (d)$1/5\text{ A}$
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Four identical cells each having an e.m.f. of 4V are connected in parallel. What will be the e.m.f. of this combination?
- (a)$1\text{ V}$
- (b)$16\text{ V}$
- (c)$1/4\text{ V}$
- (d)$4\text{ V}$
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Choose the correct option.
The potential gradient along the length of a uniform wire is 20 volt/metre. B and C are the two points at 40cm and 70cm point on a meter scale fitted along the wire. What is the potential difference between B and C?
- (a)$6\text{ V}$
- (b)$0.4\text{ V}$
- (c)$0.6\text{ V}$
- (d)$4\text{ V}$
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Study the information given and answer the questions that follow.
A torch bulb rated as 4.5 W, 1.5 V is connected as shown in figure 12 given below.
(i)[1.0]
What should be the e.m.f. of the cell required to make this bulb glow at full intensity?
- (a)$4.5\text{ V}$
- (b)$1.5\text{ V}$
- (c)$2.67\text{ V}$
- (d)$13.5\text{ V}$
(ii)[1.0]
What is the current passing through $1\ \Omega$ resistor?
- (a)$4.5\text{ A}$
- (b)$1.5\text{ A}$
- (c)$2.67\text{ A}$
- (d)$13.5\text{ A}$
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The drift velocity of a current carrying conductor is v. What will be the drift velocity if the current flowing through the wire is doubled?
- (a)$v / 4$
- (b)$v / 2$
- (c)$2v$
- (d)$4v$
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The resistance of a wire is $10\ \Omega$. It is stretched so that its length becomes four times. What will be the new resistance of the wire?
- (a)$40\ \Omega$
- (b)$160.0\ \Omega$
- (c)$120\ \Omega$
- (d)$80.0\ \Omega$
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Choose the correct option.
n identical cells each of e.m.f. E and internal resistance r are connected in parallel. An external resistance R is connected in series to this combination. The current through R is:
- (a)$\frac{nE}{R + nr}$
- (b)$\frac{nE}{nR + r}$
- (c)$\frac{E}{R + nr}$
- (d)$\frac{nE}{R + r}$
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Choose the correct option.
The figure 8 given below shows currents in a part of an electric circuit. The current i is:
- (a)$1.7\text{ A}$
- (b)$3.7\text{ A}$
- (c)$2.7\text{ A}$
- (d)$4.7\text{ A}$
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Choose the correct option.
A cell of e.m.f. E is connected to an external resistance R. The potential difference across cell is V. The internal resistance of cell will be:
- (a)$\left(\frac{E-V}{E}\right)R$
- (b)$\left(\frac{E-V}{V}\right)R$
- (c)$\left(\frac{V-E}{V}\right)R$
- (d)$\left(\frac{V-E}{E}\right)R$
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Study the information given and answer the questions that follow.
The specific resistance of manganin is $50 \times 10^{-8}\ \Omega\text{ m}$.
(i)[1.0]
The resistance of a cube of length 50m will be:
- (a)$10^{-6}\ \Omega$
- (b)$2.5 \times 10^{-5}\ \Omega$
- (c)$10^{-8}\ \Omega$
- (d)$50 \times 10^{-8}\ \Omega$
(ii)[1.0]
The specific resistance of the combination of two cubes of length 50m in series will be:
- (a)$10^{-6}\ \Omega\text{ m}$
- (b)$2.5 \times 10^{-5}\ \Omega\text{ m}$
- (c)$2 \times 10^{-6}\ \Omega\text{ m}$
- (d)$50 \times 10^{-8}\ \Omega\text{ m}$
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