Three resistances 2 Ω, 3 Ω and 4 Ω are connected in parallel. The ratio of currents passing through them when a potential difference is applied across its ends will be
5 : 4 : 3
6 : 3 : 2
4 : 3 : 2
6 : 4 : 3
Four identical cells of emf E and internal resistance r are to be connected in series. Suppose, if one of the cell is connected wrongly, the equivalent emf and effective internal resistance of the combination is
2E and 4r
4E and 4r
2E and 2r
4E and 2r
A parallel plate capacitor is charged and then isolated. The effect of increasing the plate separation on charge, potential and capacitance respectively are
constant, decreases, increases
constant, decreases, decreases
constant, increases, decreases
increases, decreases, decreases
A spherical shell of radius 10 cm is carrying a charge q. If the electric potential at distances 5 cm, 10 cm and 15 cm from the centre of the spherical shell is V1, V2 and V3 respectively, then
V1 = V2 > V3
V1 > V2 > V3
V1 = V2 < V3
V1 < V2 < V3
Three point charges 3 nC, 6 nC and 9 nC are placed at the corners of an equilateral triangle of side 0.1 m. The potential energy of the system is
991 μJ
8910 μJ
891 μJ
99100 μJ
C.
891 μJ
Given, q1 = 3 nC = 3 × 10-9 C
q2 = 6 nC = 6 × 10-9 C
q3 = 9 nC = 9 × 10-9 C
r12 = r23 = r13 = 0.1
Now, potential energy of the system,
In the circuit shown below, the ammeter and the voltmeter readings are 3A and 6V respectively. Then, the value of the resistance R is
< 2 Ω
2 Ω
≥ 2 Ω
> 2 Ω
Two cells of emf E1 and E2 are joined in opposition (such that E1 > E2). If r1 and r2 be the internal resistances and R be the external resistance, then the terminal potential difference is
A proton beam enters a magnetic field of 10-4 Wb m-2 normally. If the specific charge of the proton is 1011 C kg-1 and its velocity is 109 ms-1, then the radius of the circle described will be
100 m
0.1 m
1 m
10 m
Two concentric coils each of radius equal to 2 cm are placed at right angles to each other. If 3A and 4A are the currents flowing through the two coils respectively. The magnetic induction (in Wb m-2) at the centre of the coils will be
5 × 10-5
12 × 10-5
7 × 10-5
10-5
The resistance ofa bulb filament is 100 Ω at a temperature of 100°C. If its temperature coefficient of resistance be 0.005 per°C, then its resistance will become 200 Ω at a temperature
500°C
300°C
200°C
400°C