A group of N cells whose emf varies directly with the internal resistance as per the equation E_N = 1.5 r_N are connected as shown in the figure above. The current I in the circuit is

• 5.1 A

• 0.51 A

• 1.5 A

• 0.15 A

The temperature coefficient of resistance of a wire is 0.00125/°C. Its resistance is 1 ohm at 300 K. Its resistance will be 2 ohm at

• 1127 K

• 1400 K

• 1154 K

• 1100 K

A potentiometer has uniform potential gradient. The specific resistance of the material of the potentiometer wire is 10^-7 ohm-metre and the current passing through it is 0.1 ampere, cross-section of the wire is 10^-6 m². The potential gradient along the potentiometer wire is

• 10^-6 V/m

• 10^-4 V/m

• 10^-8 V/m

• 10^-2 V/m

A fuse wire with radius 1 mm blows at 1.5 ampere. The radius of the fuse wire of the same material to blow at 3A will be

• 3^1/4 mm

• 4^1/3 mm

• 3^1/2 mm

• 2^1/3 mm

135.

Three long straight wires A, B and C are carrying currents as shown in figure. Then the resultant force on B is directed

                     

• perpendicular to the plane of paper and outward

• perpendicular to the plane of paper and inward

• towards A

• towards C

An unknown resistance R₁ is connected in series with a resistance of 10 Ω. This combination is connected to one gap of a metre bridge while a resistance R₂ is connected in the other gap. The balance point is at 50 cm. Now, when the 10 Ω resistance is removed the balance point shifts to 40 cm. The value of R₁ is (in ohms)

• 20

• 10

• 60

• 40

In the circuit shown, the internal resistance of the cell is negligible. The steady state current in the 2 Ω resistor is

• 0.6 A

• 1.2 A

• 0.9 A

• 1.5 A

Two electnc bulbs A and B are rated as 60 W and 100 W. They are connected in parallel to the same source. Then

• B draws more current than A

• currents drawn are in the ratio of their resistances

• both draw the same current

• A draws more current than B

A wire has a resistance of 6 Ω. It is cut into two parts and both half values are connected in parallel. The new resistance is

• 3 Ω

• 6 Ω

• 12 Ω

• 1.5 Ω

The current in a simple series circuit is 5.0 amp. When an additional resistance of 2.0 ohms is inserted, the current drops to 4.0 amp. The original resistance of the circuit in ohms was

• 1.25

• 8

• 10

• 20