Sub Physics Class XII U 4 Electromagnetic Induction and Current
and U 5 Electromagnetic Waves Date 01.11.2021
MM 20 ALL QUESTIONS ARE MULTIPLE CHOICE TYPE CARRYING 1 MARK EACH Time 1hr
KNOWLEDGE BASED QUESTIONS:
1. Emf produced across the ends of a rod of length L rotating about an axis through one end of rod with angular velocity ฯ in a plane ⊥ to magnetic field of strength B is:
- (a) BL2ฯ
- (b) BL2ฯ/2
- (c) 2 BL2ฯ
- (d) BL2ฯ/4
2. Which of the following is not an application of eddy current
- (a)LED lights
- (b) dead beat galvanometer
- (c) magnetic breaking in trains
- (d) induction furnace
3. The property of coil by which counter emf is induced in it when the current through coil changes is known as
- (a) mutual inductance
- (b) self inductance
- (c) capacitance
- (d) resistance
4. The dimensions of mutual inductance is given as
- (a) M L2 T-3 A-2
- (b) M L T-2 A-2
- (c) M L T-3 A-2
- (d) M L2 T-2 A-2
5. Which rays are not portion of electromagnetic spectrum?
- (a) X-rays
- (b) Microwaves
- (c) Radio waves
- (d) ฮฒ-rays
6. Which of the following electromagnetic waves can be used to treat muscular pains?
- (a) Microwaves
- (b) Ultraviolet rays
- (c) Infrared rays
- (d) Gamma rays
7. Which of the following statements is false for the properties of electromagnetic waves?
- (a) Both electric and magnetic field vectors attain the maxima and minima at the same place and same time.
- (b) The energy in electromagnetic waves is divided equally between electric and magnetic field vectors.
- (c) Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave.
- (d) These waves do not require any material medium for propagation.
UNDERSTANDING BASED QUESTIONS:
8.If E⃗ and B⃗ represent electric field vectors of the electromagnetic waves, then the direction of the propagation of the em waves is that of
- (a) E⃗
- (b) B⃗
- (c) E⃗ x B⃗
- (d) B⃗ x E⃗
9.The pressure exerted by an em wave of intensity I (Wm-2 ) on a non-reflecting surface is (c is the velocity of light)
- (a) I/c
- (b) I × c
- (c) I × c /2
- (d) I/c2
10. What is the direction of induced current in the circular loop ABCD of radius r when a steady current of I ampere is passed through wire KL?
- (a) Clockwise ABCD
- (b) Anticlockwise ADCB
- (c) No current is induced in the loop
- (d) depends on the amount of current
11. Energy dissipates in LCR circuit in :
- (a) L only
- (b) R only
- (c) C only
- (d) All of the above
12. The capacitor acts as an infinite resistance for
- (a) DC
- (b) AC
- (c) DC as well as AC
- (d) neither AC nor DC
13. In AC circuit containing R and L, tan ฯ (where ฯ is phase difference) is equal to
- (a) R / XL
- (b) XL / R
- (c) R / Z
- (d) Z / R
14. The current amplitude versus frequency curve for an AC circuit has been drawn for three different resistors but constant values of L and C. The quality factor Q is maximum for R1 and minimum for R3. Which of the following options is correct?
- (a)R1 > R2 > R3
- (b) R1 = R2 = R3
- (c) R1 < R2 < R3
- (d) R2 = √๐ 1๐ 3
15. The variation of inductive reactance XL and capacitive reactance XC for a given inductor and capacitor versus frequency (ฮฝ) is shown by the two curves A and B as shown in figure. Here,
- (a) Curve A represents XC and curve B represents XL.
- (b) Curve A represents XL and curve B represents XC.
- (c) Both the curves are wrongly drawn. XL and XC do not depend on frequency of AC.
- (d) Curve A represents XC but curve B does not represent XL.
16. The best material for the core of a transformer, is:
- (a) stainless steel
- (b) mild steel
- (c) hard steel
- (d) soft iron
APPLICATION BASED QUESTIONS:
17. A Series LCR AC circuit contain L = 8.0 H, C = 0.5 ยตF and R = 100ฮฉ then angular resonant frequency
will be
- (a) 5 rad s -1
- (b) 50 rad s -1
- (c) 500 rad s -1
- (d) 100 rad s-1
18. Kamala peddles a stationary bicycle; the pedals of the bicycle are attached to a 100 turn coil of area 0.10 m2 . The coil rotates with angular velocity 3.14 rad s -1 and it is placed in a uniform magnetic field of 0.01 T ⊥ to the axis of rotation of the coil. The maximum voltage generated in the coil is
- (a) 314V
- (b) 31.4V
- (c) 3.14 V
- (d) 0.314V
19. The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is B0=510 nT. What is the amplitude of the electric field part of the wave? (speed of light in vacuum = 3 × 108 m/s)
- (a)133 N/C
- (b) 143 N/C
- (c) 153 N/C
- (d) 163 N/C
20. A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately
- (a) 30%
- (b) 50%
- (c) 90%
- (d) 10%
