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 ?

Resistors P and Q are connected in the gaps of the meter bridge. The balancing point is obtained $\frac{1}{3}$ m from the zero end. If a 6 Ω resistance is connected in series with P the balance point shifts to $\frac{2}{3}$ m from the same end. P and Q are

• 4, 2

• 2, 4

• both (a) and (b)

• neither (a) nor (b)

409.

The currents i₁ and i₂ through the resistors R₁ = 10 Ω and R₂ = 30 Ω in the circuit diagram with E₁ = 3 V , E₂ = 3 V and E₃ = 2 V are respectively

• 0.2 A, 0.1 A

• 0.4 A, 0.2 A

• 0.1 A, 0.2 A

• 0.2 A, 0.4 A

A milliammeter of range O - 30 mA has internal resistance of 20Ω.The resistance to be connected in series to convert it into a voltmeter of maximum reading 3V is

• 49 Ω

• 80 Ω

• 40 Ω

• 30 Ω