2018-10-01_Physics_For_You

7. If the rms current in a 50 Hz AC circuit is 5 A, the

value of the current

1

300

s aer its value becomes

zero is

(a) 52 A (b) 53 /2A

(c) 56/A (d) 52/A

8. In a series LCR circuit, resistance R = 10 : and the
   impedance Z = 10 : e phase dierence between
   the current and the voltage is
   (a) 0° (b) 30° (c) 45° (d) 60°


9. An inductor of reactance 1 : and a resistor of
   2 : are connected in series to the terminals of a
   6 V (rms) AC source. The power dissipated in the
   circuit is
   (a) 8 W (b) 12 W (c) 14.4 W (d) 18 W


10. An LCR series circuit consists of a resistance of
    10 :, a capacitor of reactance 60 : and an inductor
    coil. e circuit is found to resonate when put
    across a 300 V, 100 Hz supply. e inductance of
    coil (in H) is (take, p = 3)
    (a) 0.1 (b) 0.01 (c) 0.2 (d) 0.02


11. A circuit draws 330 W from a 110 V, 60 Hz AC line.
    e power factor is 0.6 and the current lags the
    voltage. e capacitance of a series capacitor that
    will result in a power factor of unity is equal to
    (a) 31 PF (b) 54 PF (c) 151 PF (d) 201 PF


12. A 200 km telephone wire has capacity of
    0.014 PF km–1. If it carries an alternating current
    of frequency 50 kHz, what should be the value of
    an inductance required to be connected in series so
    that impedance is minimum?
    (a) 3.6 × 10–8 H (b) 0.36 × 10–5 H
    (c) 3.6 × 10–10 H (d) 3.6 × 10–12 H
    Assertion & Reason Type

Directions : In the following questions, a statement of assertion
is followed by a statement of reason. Mark the correct choice as:
(a) If both assertion and reason are true and reason is the
correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the
correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If both assertion and reason are false.

13. Assertion : A conducting loop
    is rotated in a uniform magnetic
    eld with constant angular
    velocity Z as shown in gure. At
    time t = 0, plane of the loop is

Z

××

×

××

×

××

×

perpendicular to the magnetic eld. Induced emf

produced in the loop is maximum when plane of

loop is parallel to magnetic eld.

Reason : When plane of loop is parallel to magnetic

eld, then magnetic ux passing through the loop

is zero.

14. Assertion : An induced emf of 2 V is developed in
    a circular loop, if current in the loop is changed at
    a rate of 4 A s–1. If 4 A of current is passed through
    this loop, then ux linked with this coil will be 2 Wb.
    Reason : Flux linked with the coil is

||

/

φ=

e

di dt

i

15. Assertion : In LCR series AC circuit XL = XC = R at
    a given frequency. When frequency is doubled the

impedance of the circuit is

13

2

R.

Reason : e given frequency is resonance

frequency.

JEE MAIN / ADVANCED

Only One Option Correct Type

16. Loop A of radius r << R
    moves toward loop B with
    a constant velocity v in such
    a way that their planes are
    always parallel. What is the
    distance between the two
    loops (x) when the induced emf in loop A is
    maximum?

(a) R (b)

R

2

(c)

R

2

(d) R^1

1

2

−









17. Given L 1 = 1 mH, R 1 = 1 : , L 2 = 2 mH, R 2 = 2 :

L 1

L 2

(ii)

V

R 1 R 2

L 1 L 2

(iii)

V

R 1

R 2

L 1 L 2

(i)

R 1

V

R 2

R

Av

x

r

B