2018-10-01_Physics_For_You

1. A coil of inductance 8.4 mH and resistance 6 : is
   connected to a 12 V battery. e current in the coil
   is 1.0 A at approximately the time
   (a) 500 s (b) 20 s (c) 35 ms (d) 1 ms


2. In the circuit shown in
   gure, the A.C. source
   gives a voltage V = 20
   cos (2000 t). Neglecting
   source resistance,
   the voltmeter and
   ammeter readings will
   be
   (a) 0 V, 0.47 A (b) 1.68 V, 0.47 A
   (c) 0 V, 1.4 A (d) 5.6 V, 1.4 A


3. A resistance of 20 : is connected to a source of an
   alternating potential V = 220 sin (100 pt) V. e
   time taken by the current to change from its peak
   value to rms value, is
   (a) 0.2 s (b) 0.25 s
   (c) 25 × 10–3 s (d) 2.5 × 10–3 s


4. Two parallel vertical metallic
   rails AB and CD are separated
   by 1 m. ey are connected
   at the two ends by resistances
   R 1 and R 2 as shown in gure.
   A horizontal metallic rod of
   mass 0.2 kg slides without
   friction, vertically down
   the rails under the action
   of gravity. ere is a uniform horizontal magnetic
   field of 0.6 T perpendicular to the plane of the
   rails. When the terminal velocity is attained, the
   power dissipated in R 1 and R 2 are 0.76 W and
   1.2 W respectively. Find the terminal velocity of
   the rod and the resistance R 1 and R 2.
   (a) 1 m s–1, 0.47 :, 0.30 : (b) 2 m s–1, 0.30 :, 0.30 :
   (c) 1 m s–1, 0.47 :, 0.50 : (d) 2 m s–1, 0.30 :, 0.47 :


5. e network shown in Figure, is a part of a complete
   circuit. What is the potential dierence VB – VA,
   when the current I is 5A and is decreasing at a
   rate of 10^3 (A s–1)?

5 mHΩ 4 50 Fμ

6 Ω

A

V

FM

I

mg

R 1

A R^2 C

B D

A B

I

I 1 W 15 V5 mH

(a) 5 V (b) 15 V (c) 10 V (d) 0.5 V

6. A circular wire loop of radius R is placed in the x-y
   plane centered at the origin O. A square loop of side a
   (a << R) having two turns is placed with its center at
   z = 3 R along the axis of the circular wire loop,
   as shown in gure. e plane of the square loop
   makes an angle of 45° with respect to the z-axis. If
   the mutual inductance between the loops is given

by

μ 02

2 2

a

p/R

, then nd the value of p.

z

a

y

x

R

45°

3 R

(a) 1 (b) 3 (c) 5 (d) 7

7. At a moment (t = 0) when
   charge on capacitor C 1 is zero,
   the switch is closed. If i 0 be
   the current through inductor
   at that instant, for t > 0,nd
   the maximum charge on C 1.

(a) iC L

(^01) CC 12 +
(b) iC

L

(^02) CC 12 +
(c) i

L

(^0) CC 12 +
(d) iC

CC

(^01) L

12 +

8. A fully charged capacitor C with initial charge q 0
   is connected to a coil of self inductance L at t = 0.
   Find the time at which the energy is stored equally
   between the electric and the magnetic elds.
   (a) π
   2

LC (b)

π

4

LC (c)

π

8

LC (d) π LC

S

L

C 2

C 1