Question 13
A circular coil of radius 0.1 m consists of 10 turns. If the current flowing through the coil is
measured to be 1.5 A, what would be the magnetic field at the center of the coil? (Permeability
of free space is 4π x 10
-7
WbA
-1
m
-1
)
A. 8.5 x 10
-5
T
B. 7.42 x 10
-5
T
C. 9.42 x 10
-5
T
D. 6.32 x 10
-5
T
E. 5.52 x 10
-5
T
Correct Answer: C
Explanation:
Magnetic field at the center of a coil due to the current flowing in it is given as
B = (µ
o
/ 4 π)(2πnI / r) -------------- (1)
Putting the values in equation 1 we get
B = [(4 π x 10
-7
) / 4 π] * [(2π * 10 * 1.5)/0.1]
Or B = 10
-7
* [(2 * 3.14 * 10 * 1.5) / 0.1] (π = 3.14)
Or, B = 10
-7
* 942
Or, B = 9.42 x 10
-5
T
Hence, C is the correct answer option.
Question 14
Refractive index of diamond with respect to air is 2.4 and the refractive index of water with
respect to air is 1.33. What would be the refractive index of diamond with respect to water?
(Refractive index of air = 1)
A. 1.51
B. 0.55
C. 1.8
D. 0.75
E. 0.42
Correct Answer: C
Explanation:
Refractive index of one medium with respect to another medium is given as
2
μ
1
= μ
2
/ μ
1
Here we have been given refractive index of diamond with respect to air = 2.4 i.e.
2.4 = μ
diamond
/1 Or μ
diamond
= 2.4
Also, refractive index of water with respect to air = 1.33 i.e.
1.33 = μ
water
/1 Or μ
water
= 1.33
Thus, refractive index of diamond with respect to water becomes
diamond
μ
water
= 2.4 / 1.33
