Force on a Current-Carrying Conductor in a Magnetic Field

Question 1

What is a d.c. motor and how does it work?

Answer 1

A direct current (d.c.) motor converts electrical energy into mechanical energy using a rotating coil in a magnetic field. The motor works based on the interaction of the current in the coil with the magnetic field, creating a force that causes the coil to rotate.

Question 2

What are electromagnets?

Answer 2

Electromagnets are created by winding a coil of wire around a ferromagnetic core (e.g., iron). When current passes through the coil, a magnetic field is generated, turning the core into a magnet. Electromagnets are used in applications like relays, electric bells, and maglev trains.

Question 2

What is the principle of a carbon microphone?

Answer 2

A carbon microphone works by varying the resistance of a carbon granule transmitter in response to sound waves. The varying resistance changes the electrical current, creating an electrical signal that corresponds to the sound.

Question 2

What are moving coil and moving iron instruments?

Answer 2

• Moving Coil Instruments: Measure electrical quantities by using a coil suspended in a magnetic field. The coil moves in response to the current, and the movement is used to indicate the measurement.
• Moving Iron Instruments: Measure electrical quantities using a piece of iron that moves in response to the magnetic field created by the current. The movement is then translated into a measurement.

Question 3

How do you convert a galvanometer into an ammeter or a voltmeter?

Answer 3

• Ammeter: To convert a galvanometer into an ammeter, a low-value resistor (shunt) is connected in parallel with the galvanometer. This allows most of the current to pass through the shunt, with only a small fraction passing through the galvanometer.
• Voltmeter: To convert a galvanometer into a voltmeter, a high-value resistor (multiplier) is connected in series with the galvanometer. This allows the galvanometer to measure voltage by having a high resistance that limits the current.

Question 4

What factors affect the sensitivity of a galvanometer?

Answer 4

The sensitivity of a galvanometer is affected by:

• The strength of the magnetic field: A stronger magnetic field increases sensitivity.
• The number of turns in the coil: More turns increase sensitivity.
• The spring constant: A lower spring constant increases sensitivity.
• The coil’s area: A larger coil area increases sensitivity.