The wire loop PQRSP formed by joining two semicircular wires of radii R1 & R2 carries a current I as shown in the figure. The magnitude of the magnetic field at the centre 'C' is:
(μ0I / 4) (1/R1 - 1/R2)
The magnetic field at the center (C) of a circular loop due to a semicircle of radius R carrying current I is given by:
B = (μ0 I) / (4R).
- The two semicircles have radii R1 and R2, and they carry current in opposite directions.
- The net magnetic field at C is obtained by subtracting the fields due to the two semicircles:
B = (μ0I / 4) (1/R1 - 1/R2).
Thus, the correct answer is (d).
Important Questions from Electromagnetic Induction
In a pair of adjacent coils, for a change of current in one of the coils from 0 A to 10 A in 0.25 s, the magnetic flux in the adjacent coil changes by 15 Wb. The mutual inductance of the coils is:
A 50 Hz AC current of crest value 1 A flows through the primary of a transformer. If the mutual inductance between the primary and secondary is 0.5 H, the crest voltage induced in the secondary is:
A long solenoid of diameter 0.1 m has 2 × 104 turns per meter. At the center of the solenoid, a coil of 100 turns and radius 0.01 m is placed with its axis coinciding with the solenoid axis. The current in the solenoid reduces at a constant rate to 0 A from 4 A in 0.05 s. If the resistance of the coil is 10π² Ω, then the total charge flowing through the coil during this time is:
Lower half of a convex lens is made opaque. Which of the following statements describes the image of the object placed in front of the lens?
A transformer has an efficiency of 80%. It works at 3 kW and 120 V. If the secondary voltage is 240 V, what will be the secondary current?
