UNIT
2 – CURRENT ELECTRICITY
2025
1. When
a battery is connected between the terminals P and Q, as shown in Figure 1
below, it is found that no current flows through 5Ω resistor. Then, the value
of resistor X is:
(a) 10 Ω (c) 25 Ω (b)
20 Ω (d) 45 Ω
2. Figures
4 and 5 represent the combination of two identical cells having negligible
internal resistance.
(a) In which of the two combinations,
emf of the battery is greater?
(b) When a resistor ‘R’ is connected
between the terminals P and Q, I1 and I2 are the currents
flowing through ‘R’ in Figure 4 and Figure 5 respectively. Obtain the ratio
I1/ I2
3. Figure
6 below shows an electric circuit.
Apply Kirchhoff’s laws to calculate:
(a) current ‘I’ flowing through the 2
Ω resistor.
(b) emf of the cell ‘E’.
4. In
a potentiometer experiment, a cell of emf 1.25 V gives a balance point at 35 cm
mark of the wire. If this cell is replaced by another cell, the balance point
is at 63 cm mark. Calculate the emf of the second cell.
5. 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) Identify the instruments X and Y.
(b) Using the graph of V against I
shown below, calculate;
(1) emf (E) of the cell.
(2) Internal resistance (r) of the
cell.
6. The
graph below shows the variation of current density (J) with electric field (E)
applied to two different metallic wires A and B.
(a) Which one of the wires, A or B,
has higher resistivity?
(b) For a certain value of electric
field (E), in which wire ‘A’ or ‘B’ is drift velocity greater? Give a reason
for your answer.
2024
7. If
potential difference between the two ends of a metallic wire is doubled, drift
speed of free electrons in the wire
(a) remains
same. (b) becomes double (c) becomes four times. (d) becomes half.
8. A
metre bridge is balanced with a known resistance (R) in the left hand gap and
an unknown resistance (S) in the right hand gap. Balance point is found to be
at a distance of l cm from the left hand side. When the battery and the
galvanometer are interchanged, balance point will
(a) shift towards left.
(b) shift towards right.
(c) remain same.
(d) shift towards left or right
depending on the values of R and S
9. Three
identical cells each of emf ‘e‘ are connected in parallel to form a battery.
What is the emf of the battery?
10. Three
bulbs B1(230V, 40W), B2(230V, 60W) and B3(230V, 100W) are connected in series
to a 230V supply. Which bulb glows the brightest?
11. Figure
2 below shows two batteries E1 and E2 having emfs of 18V and 10V and internal
resistances of 1Ω and 2Ω respectively. W1, W2 and W3 are uniform metallic wires
AC, FD and BE having resistance of 8Ω, 6Ω and 10Ω respectively. B and E are
midpoints of the wires W1 and W2. Using Kirchhoffs laws of electrical circuits,
calculate the current flowing in the wire W3
12. Figure
3 below shows a potentiometer circuit in which the driver cell D has an emf of
6 V and internal resistance of 2Ω. The potentiometer wire AB is 10m long and
has a resistance of 28Ω. The series resistance Rs is of 20Ω.
Calculate:
(a) The current Ip flowing in the
potentiometer wire AB when the jockey (J) does not touch the wire AB.
(b) emf of the cell X if the
balancing length AC is 4·5m
13. (b)
(1)RMS value of an alternating current flowing in a circuit is 5A. Calculate
its peak value.
(2) State any one difference between
a direct current (dc) and an alternating current (ac).
2023
14. 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:
15. In case of metals, what is the relation between current
density (J), electrical conductivity (s) and electric field intensity (E)?
16. . (i) Write balancing condition of a Wheatstone bridge.
(ii) Current ‘I’
flowing through a metallic wire is related to drift speed Vd of free
electrons as follows: I = nAevd State what the symbol ‘n’ stands for
17. Eight identical cells, each of emf 2V and internal resistance
3W, 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 6W. Calculate:
(a) emf of the
battery.
(b) internal
resistance of the battery.
(c) current flowing
through R.
18. In the circuit shown in Figure 3 below, E1 and E2 are
batteries having emfs of 25V and 26V. They have an internal resistance of 1Ω
and 5Ω respectively. Applying Kirchhoff’s laws of electrical networks,
calculate the currents I1 and I2
2022
19. Specific resistance of the material of a wire depends on:
(a) Length of the
wire. (b) Area of cross section
of the wire.
(c) Volume of the
wire. (d) Temperature of the
wire.
20. Two electric bulbs, whose resistances are in the ratio 1:2,
are connected in parallel to a constant voltage supply. The powers dissipated
in them are in the ratio:
(a) 1 : 1 (b) 1 : 2
(c) 2 : 1 (d) 1 : 4
21. When a potential difference of 2 V is applied between the two
ends of a 1 m long and uniform metallic wire, current density in it is found to
be 4 × 106 Am–2 . Resistivity of the material of the wire is:
(a) 5 × 10–7 Ωm
(b) 5 × 10–8 Ωm
(c) 5 × 106
Ωm (d) 5 × 108 Ωm
22. SI unit of electrical conductivity is
23. If a variable resistance is connected to a cell of constant
emf, then the graph which represents the correct relationship between current I
and resistance R is:
24. A battery sends a current of 1.5 A through an external
resistance of 1.0 W. If the internal resistance of the battery is 0.5 W, its
emf is:
(a) 2.00 V (b) 2.25 V (c) 2.50 V (d)
2.75 V
25. N identical cells each of emf ‘e’ and internal resistance ‘r’
are connected in series to form a row. M such rows are connected in parallel to
form a battery. When an external resistance R is connected to the battery,
current flowing through it is
26. Kirchhoff’s junction rule is based on the principle of
conservation of:
(a) energy (b) charge (c) momentum (d)
momentum and energy
27. Wheatstone bridge principle is used to measure:
(a) Resistance of a
wire (b) Potential
difference across a resistor.
(c) Current flowing
through a wire. (d) Emf of a cell
28. In a potentiometer, balancing length with a standard cell of
emf 1.08 V is 21.6 cm. Balancing length with a cell of emf 1.50 V will be
(a) 21.6 cm (b) 30.0 cm (c) 45.0 cm (d) 60.0 cm
29. If potential difference across 80 cm of a potentiometer wire
is 2 V, potential gradient across the wire is
(a) 0.025 Vm–1
(b) 0.050 Vm–1 (c) 0.075 Vm–1 (d) 2.50 Vm–1
30. In the Wheatstone bridge circuit shown below, P = 10 W, Q =
20 W, R = 200 W and S = 100 W, emf of the battery being 2 V. The current
flowing through the galvanometer is:
(a) 0 (b) 1 A (c) 2 A (d)
3 A
31. An electric bulb is marked 200 V, 50 W. If it is used on a
400 V supply, it will draw a current of:
(a) 0.25 A (b) 0.40 A (c) 0.50 A (d)
0.80 A
2020
32. A uniform copper wire having a cross sectional area of 1 mm2
carries a current of 5 A. Calculate the drift speed of free electrons in it.
(Free electron number density of copper = 2 × 1028/m3.)
33. An electric bulb is rated as 250V, 750Ω. Calculate the :
(i)
Electric current flowing
through it, when it is operated on a 250V supply.
(ii)
(ii) Resistance of its
filament.
34. E1 and E2 are two batteries having emfs of 3V and 4V and
internal resistances of 2Ω and 1Ω respectively. They are connected as shown in
Figure 2. Using Kirchhoff's Laws of electrical circuits, calculate the currents
I1 and I2.
35. A potentiometer circuit is shown in Figure 3. AB is a uniform
metallic wire having length of 2 m and resistance of 8Ω. The batteries E1 and
E2 have emfs of 4V and 1.5V and their internal resistance are 1Ω and 2Ω
respectively
(i) When the jockey
J does not touch the wire AB, calculate :
(a) the current
flowing through the potentiometer wire AB.
(b) the potential
gradient across the wire AB.
(ii) If, the jockey
J is made to touch the wire AB at a point C such that the galvanometer (G)
shows no deflection. Calculate the length AC
2019
36. Calculate the net emf across A and B shown in Figure 1 below
37. In a potentiometer experiment, the balancing length with a
resistance of 2 W. is found to be 100 cm, while that of an unknown resistance
is 500 cm. Calculate the value of the unknown resistance.
38. Obtain the balancing condition for the Wheat stone bridge
arrangement.
39. Draw a labelled circuit diagram of a potentiometer to measure
the internal resistance ‘r’ of a cell. Write the working formula (derivation is
not required).
40. In a potentiometer experiment, balancing length is found to
be 120 cm for a cell E1 of emf 2V. What will be the balancing length for
another cell E2 of emf 1.5V? (No other changes are made in the experiment.)
41. e1 and e2 are two batteries having emf of 34V and 10V
respectively and internal resistance of 1Ω and 2Ω respectively. They are
connected as shown in Figure given below. Using Kirchhoffs’ Laws of electrical
networks, calculate the currents I1 and I2.
42.
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