Advertisements
Advertisements
Question
A long solenoid with 15 turns per cm has a small loop of area 2.0 cm2 placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from 2.0 A to 4.0 A in 0.1 s, what is the induced emf in the loop while the current is changing?
Advertisements
Solution
Number of turns on the solenoid = 15 turns/cm = 1500 turns/m
Number of turns per unit length, n = 1500 turns
The solenoid has a small loop of area, A = 2.0 cm2
= 2 × 10−4 m2
Current carried by the solenoid changes from 2 A to 4 A.
∴ Change in current in the solenoid, di = 4 − 2 = 2 A
Change in time, dt = 0.1 s
Induced emf in the solenoid is given by Faraday’s law as:
`"e" = ("d"phi)/("dt")` ........(1)
Where,
`phi` = Induced flux through the small loop = BA ...........(2)
B = Magnetic field = `mu_0"ni"` .....(3)
μ0 = Permeability of free space
= 4π × 10−7 H/m
Hence, equation (1) reduces to:
`"e" = "d"/("dt")("BA")`
= `"A"mu_0"n" xx (("di")/("dt"))`
= `2 xx 10^-4 xx 4pi xx 10^-7 xx 1500 xx 2/0.1`
= 7.54 × 10−6 V
Hence, the induced voltage in the loop is 7.54 × 10−6 V.
APPEARS IN
RELATED QUESTIONS
Explain the meaning of the term mutual inductance.
An air-cored solenoid with length 30 cm, area of cross-section 25 cm2 and number of turns 500, carries a current of 2.5 A. The current is suddenly switched off in a brief time of 10−3 s. How much is the average back emf induced across the ends of the open switch in the circuit? Ignore the variation in magnetic field near the ends of the solenoid.
Define coefficient of mutual induction.
Consider two concentric circular coils, one of radius r1 and the other of radius r2 (r1 < r2) placed coaxially with centers coinciding with each other. Obtain the expression for the mutual inductance of the arrangement.
A coil of self-inductance 2.5H and resistance 20Ω is connected to a battery of emf 120V having the internal resistance of 5 n. Find:
1) The time constant of the circuit.
2) The current in the circuit in steady state
Two circular loops are placed with their centres separated by a fixed distance. How would you orient the loops to have (a) the largest mutual inductance (b) the smallest mutual inductance?
A solenoid of length 20 cm, area of cross-section 4.0 cm2 and having 4000 turns is placed inside another solenoid of 2000 turns having a cross-sectional area 8.0 cm2 and length 10 cm. Find the mutual inductance between the solenoids.
A pair of the adjacent coil has a mutual inductance of 1.5 H. If the current in one coil varies from 0 to 20 A in 0.5 s, what is the change of flux linked with the other coil.
Two coils P and Q are kept near each other. When no current flows through coil P and current increases in coil Q at the rate 10 A/s, the e.m.f. in coil P is 20 mV. When coil Q carries no current and current of 1.6 A flows through coil P, the magnetic flux linked with the coil Q is ____________.
In an induction coil, the coefficient of mutual inductance is 6 henry. If a current of 10 ampere in the primary coil is cut-off in `1/1500"s"`, the e.m.f. at the terminals of the secondary coil will be ____________.
The mutual inductance between two coils is 0.09 henry. If the current in the primary coil changes from 0 to 20 A in 0.006 s, the e.m.f. induced in the secondary coil at that instant is ____________.
The mutual inductance of a pair of coils is 0.75 H. If current in the primary coil changes from 0.5 A to zero in 0.01 s, find average induced e.m.f. in secondary coil ______.
If number of turns in primary and secondary coils is increased to two times each, the mutual inductance ______.
Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon the ______.
Two conducting circular loops of radii R1 and R2 are placed in the same plane with their centres coinciding. If R1 > > R2, the mutual inductance M between them will be directly proportional to ______.
A toroid is a long coil of wire wound over a circular core. The major radius and cross-sectional radius of the toroid are R and r, respectively. The coefficient of mutual induction of the toroid is ______.
(The magnetic field in it is uniform, N = number of turns, R >> r, μ0 = permeability of free space)
Write the S.I. unit of mutual inductance.
Two coils having self inductances L1 = 75 mH and L2 = 55 mH are coupled with each other. The coefficient of coupling (K) is 0. 75. Calculate the mutual inductance (M) of the two coils
Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon ______.
