NEET Practice Questions (MCQs) with Answers & Solutions

When a current in a coil changes, it induces a back emf in the same coil. The self-induced emf is given by $\epsilon = -L \frac{dI}{dt}$. L is the self-inductance of the coil. It is a measure of the inertia of the coil against the change of current through it.

The SI unit of magnetic flux is weber (Wb) or tesla meter squared (T m$^2$).

In an ac generator, mechanical energy is converted to electrical energy by virtue of electromagnetic induction.

The magnetic flux through a surface of area A placed in a uniform magnetic field B is defined as, $\Phi_B = B \cdot A = BA \cos \theta$ where $\theta$ is the angle between B and A.

Further, the deflection (and hence current) is found to be larger when the magnet is pushed towards or pulled away from the coil faster. This is because a faster motion leads to a greater rate of change of magnetic flux, leading to a larger induced emf and thus a larger current.

When the key is held pressed, current in coil C2 is constant. Therefore, there is no change in the magnetic flux through coil C1 and the current in C1 will be zero (and consequently no induced emf).

The total amount of work done in establishing the current I (and thus the magnetic energy stored) is $W = \frac{1}{2}LI^2$.

In the case of a stationary conductor, the force on its charges is given by $F = q(E + v \times B)$. Since $v = 0$, any force on the charge must arise from the electric field term E alone. Therefore, to explain the existence of induced emf or induced current, we must assume that a time-varying magnetic field generates an electric field.

Haloarenes contain a halogen atom(s) attached to sp$^2$ hybridised carbon atom(s) of an aryl group.

Halogen atoms are more electronegative than carbon, therefore, carbon-halogen bond of alkyl halide is polarised. This electronegativity difference is the primary factor influencing the polarity.