List of top Physics Questions on Electric Current And Circuit

Define electromotive force of a cell.
In the given circuit, find out the equivalent resistances across the points A and B when:
(i) \(V_A > V_B\), (ii) \(V_A < V_B\).
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An electron in hydrogen atom is moving round the nucleus with speed \(2.2 \times 10^6\) m/s in an orbit of radius \(5 \times 10^{-11}\) meter. Find the value of equivalent electric current.
What is the phenomenon of mutual induction? What is meant by 1 henry mutual inductance? If a current of 4 A is reduced to zero in 10 \(\mu\)s in the primary coil of a transformer, then 40 kV of induced e.m.f. is produced in the secondary coil. Find out the mutual inductance between the primary and the secondary coils.
What is the working principle of a transformer? The ratio of the number of turns in the primary and secondary coils in an ideal step-down transformer is 20 : 1. When input voltage of 250 V is applied, then the output current is 8 A. Calculate:
i) Current in the primary coil
ii) Output power
What is meant by wattless current?
On connecting a cell of e.m.f. 0.5 volt with an external resistance of 1.9 $\Omega$, the current flowing is 0.75 A. The internal resistance of the cell is:

A current is passed in a wire of \( 4 \, \Omega \) resistance by a battery. Find out the internal resistance of the battery, when current is passed in another \( 9 \, \Omega \) resistor by the same battery; while the same heat is produced during the same time in both wires. 
 

A wire loop PQRSP formed by joining two semicircular wires of radii R1, and R2 carries a current I as shown in figure below. The magnitude of magnetic induction at centre C is
two semicircular wires-carries a current