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Practice Test - Physics 21

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Question 1

A fully charged capacitor C with initial charge q₀ is connected to a coil of self-inductance L at t = 0. The time at which the energy is stored equally between the electric and the magnetic fields is

Question 2

If radius of

nucleus is estimated to be 3.6 Fermi then the radius

nucleus be nearly

Question 3

The thermo e.m.f. of a thermo-couple is 25 μV/°C at room temperature. A galvanometer of 40 ohm resistance, capable of detecting current as low as 10⁻⁵ A, is connected with the thermocouple. The smallest temperature difference that can be detected by this system is

Question 4

The anode voltage of a photocell is kept fixed. The wavelength l of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows:

Question 5

A thin semi–circular ring of radius r has a positive charge q distributed uniformly over it. The net field

at the center O is

Question 6

Two insulating plates are both uniformly charged in such a way that the potential difference between them is V₂ – V₁ = 20 V. (i.e. plate 2 is at a higher potential). The plates are separated by d = 0.1 m and can be treated as infinitely large. An electron is released from rest on the inner surface of plate 1. What is its speed when it hits plate 2 ?
(e = 1.6 × 10^-19C, m_e = 9.11 × 10^-31 kg)

Question 7

In an oscillating LC circuit the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic field is

Question 8

Two bodies of masses m and 4 m are placed at a distance r. The gravitational potential at a point on the line joining them where the gravitational field is zero is

Question 9

The resultant of forces and is . If is doubled then is doubled. If the direction of is reversed, then is again doubled. Then P² : Q² : R² is

Question 10

If the terminal speed of a sphere of gold (density = 19.5 kg /m³) is 0.2 m/s in a viscous liquid (density = 1.5 kg/m³), find the terminal speed of a sphere of silver (density = 10.5 kg/m³) of the same size in the same liquid.

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Jun 15JEE & BITSAT