31.

Arrange the following electromagnetic radiation in the order of decreasing energy.

A. Infrared waves         B. Ultraviolet rays

C. Orange light             D. Green light

• B, C, A, D

• D, A, C, B

• B, D, C, A

• A, C, D, B

In the circuit, shown in figure, K is open. The charge on capacitor C in steady state is q. Now, key is closed and at steady state, the charge on C is q₂ the ratio of charges $\left(\frac{{\mathrm{q}}_1}{{\mathrm{q}}_2}\right)$ is 

• $\frac{3}{2}$

• $\frac{2}{3}$

• 1

• $\frac{1}{2}$

When an AC source of emf e = E₀ sin (100t) is connected across a circuit, the phase difference between the emf e and the current i in the circuit is observed to be $\mathrm{\pi }$/4, as shown in the diagram. If the circuit consists possibly only of R-C or R-L or L-C is series, find the relationship between the two elements.

• R = 1 kΩ , C = 10 µF

• R = 1 kΩ , C = 1 µF

• R = 1 kΩ , L = 10 H

• R = 1 kΩ , L = 1 H

For the circuit shown in figure, the voltage across 4 Ω resistance is

• 1 V

• 2 V

• 4 V

• 5 V

Three solenoid coils of same dimensions, same number of turns and same number of layers of windings are taken. Coil 1 with inductance L₁ was wound using a wire of resistance 11 Ω /m, coil 2 with inductance L₂ was wound using the similar wire but the direction of winding was reversed in each layer, coil 3 with inductance L₃ was wound using a superconducting wire. The self inductance of the coils L₁ , L₂ and L₃ are

• L₁ = L₂ = L₃

• L₁ = L₂ , L₃ = 0

• L₁ = L₃ , L₂ = 0

• L₁ > L₂ > L₃

A long hollow conducting cylinder is kept co-axially inside  another long and hollow conducting cylinder of larger  radius. Both the cylinders are initially electrically neutral.Now consider the following statements

1. A potential difference appears between the two cylinders when a charge density is given to the inner cylinder.
2. A potential difference appears between the two cylinders when a charge density is given to the outer cylinder.
3. No potential difference appears between the two cylinders when a uniform line
   charge is kept along the axis of cylinders.
4. No potential difference appears between the two cylinders when same charge
   density is given to both the cylinders.

Which of the above mentioned statement is/are correct?

• Only I

• I, IV

• Only II

• Only III

An iron rod of volume 10^-4 m³ and relative permeability 1000 is placed inside a long solenoid having 5 turns/cm. If a current of 5.0 A is passed through the solenoid, then magnetic moment of the rod is

• 20 A-m²

• 25 A-m²

• 30 A-m²

• 35 A-m²

Two electric bulbs rated 50W and 100W are glowing at full power, when used in parallel with a battery of emf 120 V and internal resistance 10 Ω. The maximum number of bulbs that can be connected in the circuit when glowing at full power is

• 6

• 4

• 2

• 8

A LED has a voltage drop of 2V across it and passes a current of 10 mA. When it operates with a 6V battery through a limiting resistor R. The value of R is

• 40 kΩ

• 200 Ω

• 4 kΩ

• 400 Ω

In a region, the potential is represented by V (x,y,z) = 6x − 8xy − 8y + 6yz where V is in volts and x,y,z are in meters. The electric force experienced by a charge of 2C situated at point (1,1,1) is

• $6\sqrt{5} \mathrm{N}$

• 30 N

• 24 N

• $4\sqrt{35} \mathrm{N}$