The resistance of an incandescent lamp is

• smaller when switched on

• greater when switched off

• the same whether it is switch off or switch on

• greater when switched on

212.

An ammeter and a voltmeter are joined in series to a cell. Their readings are A and V respectively. If a resistance is now joined in parallel with the voltmeter, then

• A will decrease, V will increase

• A will increase, V will decrease

• both A and V will increase

• both A and V will decrease

If each of the resistance of the network shown in figure is R, the equivalent resistance between A and B is

• 3R

• 5R

• $\frac{\mathrm{R}}{2}$

• R

A cell supplies a current of 0.9 A through a 2 Ω resistor and a current of 0.3 A through a 7 Ω resistor. The internal resistance of the cell is

• 1.2 Ω

• 2.0 Ω

• 0.5 Ω

• 1.0 Ω

A and B are two conductors carrying a current I in the same direction. x and y are two electron beams moving in the same direction. Then there will be

• attraction between A and B, repulsion between x and y

• repulsion between A and B, attraction between x and y

• attraction between A and B and x and y

• repulsion between A and B and x and y

The current-voltage graph for a given metallic conductor at two different temperature T₁ and T₂ are as shown in the figure. Then

• T₁ < T₂

• nothing can be said about T₁ and T₂

• T₁ = T₂

• T₁ > T₂

The current-voltage graph for a given metallic conductor at two different temperature T₁ and T₂ are as shown in the figure. Then

• T₁ < T₂

• nothing can be said about T₁ and T₂

• T₁ = T₂

• T₁ > T₂

A non -conducting ring of radius 0.5m carries a total charge of 1.11 x 10^-10 C distributed non-uniformly on its circumference producing on its circumference on the electric field. E everywhere is space.

The value of the line integral ${\int }_{l = \infty }^{l = 0} (-E.dl)$ (l = 0 being centre of ring) in volts is

• +2

• -1

• -2

• zero

a potentiometer wire is 100 cm long and a constant potential difference is maintained across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf is,

• 5:4

• 3:4

• 3:2

• 3:2

A square loop of ABCD carrying a current i, is placed near and coplanar with a long straight conductor XY carrying a current I, the net force on the loop will be