Current Electricity

Which of the following set up can be used to verify the Ohm's law ?

A uniform wire of resistance R and length L is cut into four equal parts, each of length L/4, which are then connected in parallel combination. The effective resistance of the combination will be 

• R

• 4R

• $\frac{\mathrm{R}}{4}$

• $\frac{\mathrm{R}}{16}$

Two identical cells of the same emf and same internal resistance give the same current through an external resistance 22, regardless of whether they are connected in series or parallel. The internal resistance of the cell is

• 1 Ω

• 2 Ω

• 3 Ω

• 4 Ω

Six equal resistance are connected between points P, Q and R as shown in the figure. Then the net resistance will be maximum between

• P and Q

• Q and R

• P and Q

• only two points

The equivalent resistance across A and B is

• 2 Ω

• 3 Ω

• 4 Ω

• 5 Ω

For the post office box arrangement to determine the value of unknown resistance, the unknown resistance should be connected between

• B and C

• C and D

• A and D

• B₁ and C₁

The figure shows variation of photocurrent with anode potential for a photo- sensitive surface for three different radiations. Let I_a , l_b and I_c be the intensities and v_a , v_b and v_c , be the frequencies for the curves a, b and c respectively. Then

• v_a = v_b and I_a ≠ I_b

• v_a = v_c and I_a = I_c

• v_a = v_b and I_a = I_b

• v_b = v_c and I_b = I_c

In the given circuit the equivalent resistance between the points A and B in ohms is

• 9

• 11.6

• 14.5

• 21.2

In the electric circuit shown each cell has an emf of 2 V and internal resistance of 1Ω. The external resistance is 2Ω. The value of the current I is (in amperes)

• 2

• 1.25 Ω

• 0.4

• 1.2

Which of the following graphs represent variation of magnetic field B with distance r for a straight long wire carrying current ?