Physics MCQs for NEET — Practice Questions with Answers

The text states, 'In order to show phase relationship between voltage and current in an ac circuit, we use the notion of phasors. The analysis of an ac circuit is facilitated by the use of a phasor diagram.'

From the section 'AC VOLTAGE APPLIED TO AN INDUCTOR', it is stated that 'the self-induced Faraday emf in the inductor' is $L \frac{di}{dt}$. Applying Kirchhoff's loop rule for a pure inductor, $v - L \frac{di}{dt} = 0$, hence $v = L \frac{di}{dt}$.

Example 7.5 states, 'As the iron rod is inserted, the magnetic field inside the coil magnetizes the iron increasing the magnetic field inside it. Hence, the inductance of the coil increases. Consequently, the inductive reactance of the coil increases.'

As per Example 7.5: 'As a result, a larger fraction of the applied ac voltage appears across the inductor, leaving less voltage across the bulb. Therefore, the glow of the light bulb decreases.'

The text mentions, 'Usually, inductors have appreciable resistance in their windings, but we shall assume that this inductor has negligible resistance' (for the purpose of an ideal purely inductive circuit analysis).

According to Maxwell's theory, accelerated charges radiate electromagnetic waves. Neither stationary charges nor charges in uniform motion can be sources of electromagnetic waves. (Context: 'It is an important result of Maxwell’s theory that accelerated charges radiate electromagnetic waves.')

From Maxwell's equations, it is seen that the magnitude of the electric and the magnetic fields in an electromagnetic wave are related as $B_0 = (E_0/c)$, which rearranges to $E_0 = B_0c$. (Context: 'It is also seen from Maxwell’s equations that the magnitude of the electric and the magnetic fields in an electromagnetic wave are related as $B_0 = (E_0/c)$ (8.10)')

In a material medium of permittivity $\epsilon$ and magnetic permeability $\mu$, the velocity of light becomes $v = 1/\sqrt{\mu\epsilon}$. (Context: '...the velocity of light becomes, $1/v = \mu\epsilon$ (8.11)')

Maxwell's equations in vacuum include Gauss's Law for electricity, Gauss's Law for magnetism, Faraday's Law, and Ampere-Maxwell Law. Kirchhoff's Current Law is a fundamental principle in circuit analysis, but not one of Maxwell's fundamental equations for electromagnetic fields. (Context: 'MAXWELL’S EQUATIONS IN VACUUM: 1. “E.dA = Q/ε0 (Gauss’s Law for electricity) 2. “B.dA = 0 (Gauss’s Law for magnetism) 3. “E.dl = – d/dt ΦB (Faraday’s Law) 4. “B.dl == µ0i + µ0ε0 d/dt ΦE (Ampere – Maxwell Law)')

Maxwell suggested the existence of an additional current, called displacement current, due to time-varying electric field and is given by $I_d = \epsilon_0 d\Phi_E/dt$. (Context: 'This displacement current is due to time-varying electric field and is given by $\epsilon_0 d\Phi_E/dt$')