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.

Explanation

When a wire is placed perpendicular to a magnetic field, the force on the wire is proportional to the current flowing through it.

If the current increases, the force on the wire will also increase.

Explanation

A magnetic compass is a device that responds to the presence of a magnetic field by aligning its needle with the direction of the field.

It is a common tool used to detect and measure magnetic fields.

Explanation

Magnetic poles always exist in pairs, with every magnet having a north pole and a south pole.

Like poles (north-north or south-south) repel each other.

Unlike poles (north-south or south-north) attract each other.

Explanation

A battery is connected in an electric circuit to provide a constant potential difference (voltage) across the circuit, allowing electric current to flow through the conductors.

The battery maintains a constant voltage, ensuring a consistent flow of current through the circuit.

Explanation

Resistance is the property of a material or object that opposes the flow of electric charge (current) through it.

It is measured in ohms (Ω) and depends on the material, length, and cross-sectional area of the object.

Explanation

When two resistances are connected in parallel, the net resistance (Rnet) is calculated using the formula:

1/Rnet = 1/R1 + 1/R2

where R1 and R2 are the individual resistances.

In this case, R1 = 6 Ω and R2 = 12 Ω, so:

1/Rnet = 1/6 + 1/12 = 1/4

Rnet = 4 Ω

Therefore, the net resistance of the two resistances connected in parallel is 4 Ω.

Explanation

Ohm's law is not applicable to Semiconductors, as the relationship between voltage and current does not remain constant in these devices.

Semiconductors have a non-linear current-voltage characteristic, making Ohm's law inapplicable.

Explanation

Ohm's Law is valid only if the temperature of the conductor remains constant.

If the temperature changes, the resistance of the conductor may change, and Ohm's Law may not hold.