Explanation

Thermionic emission is the process by which electrons are emitted from a hot metal surface.

This occurs when a metal is heated to a high temperature, causing the electrons to gain enough energy to escape from the metal's surface.

This process is also known as thermal electron emission or Edison effect.

Explanation

If the direction of the magnetic field is reversed, the direction of the force exerted on a charged particle or a current-carrying wire will also be reversed.

This is because the force due to a magnetic field depends on the direction of the field.

The direction of the current or velocity, and the charge of the particle (if applicable).

Explanation

Electric fields can be detected by electrons, which are charged particles that respond to the force exerted by the electric field.

Electrons will accelerate or decelerate in the presence of an electric field, allowing for the detection of the field.

Explanation

A filament is a thin wire, typically made of tungsten, that is heated to produce a continuous flow of electrons.

When an electric current is passed through the filament, it heats up and releases electrons, creating a steady stream of electrons.

This principle is used in various devices such as vacuum tubes, cathode ray tubes (CRTs), and electron microscopes.

Explanation

Metals are good conductors of electricity because they have free electrons, also known as conduction electrons or mobile electrons.

These electrons are not tightly bound to a specific atom and are free to move throughout the metal, carrying electrical current.

Explanation

A turn ratio of 10 means that the secondary coil (Ns) has 10 times more turns than the primary coil (Np).

This is a step-up transformer, which increases the voltage and decreases the current.

Explanation

A step-up transformer increases the voltage of the input signal, resulting in a higher voltage output.

This is achieved by having more turns in the secondary coil than in the primary coil.

Explanation

The direction of induced e.m.f. (electromotive force) in a circuit is determined by Lenz's law.

It states that the induced e.m.f. will oppose the change in magnetic flux that induced it.

This is a consequence of the conservation of energy.

Explanation

The commutator is a crucial component in a DC motor that reverses the direction of current through the coil every half-cycle.

It is a mechanical switch that rotates with the armature.

It makes contact with the brushes, switching the current flow to the coil as the armature rotates.

Explanation

A DC motor is an electrical machine that converts electrical energy into mechanical energy.

It uses electrical current to generate a magnetic field that interacts with the motor's magnets.

It causing the motor to rotate and produce mechanical energy.