Electricity and Magnetism - SS1 Physics Past Questions and Answers - page 3
Discuss the effects of changing the velocity, charge, and magnetic field strength on the magnetic force experienced by a charged particle.
Changing the velocity of a charged particle affects the magnitude of the magnetic force but not its direction. Doubling the velocity doubles the magnitude of the magnetic force. Changing the charge of the particle also affects the magnitude of the magnetic force. Doubling the charge doubles the magnitude of the force. Finally, changing the magnetic field strength affects both the magnitude and direction of the magnetic force. Doubling the magnetic field strength doubles the magnitude of the force, and changing the direction of the magnetic field changes the direction of the force.
Electromagnetic induction is the process of generating an electromotive force (emf) in a conductor by:
Applying a magnetic field to the conductor
Applying an electric field to the conductor
Moving the conductor relative to a magnetic field
Changing the temperature of the conductor
According to Faraday's law of electromagnetic induction, the magnitude of the induced emf in a conductor is directly proportional to:
The resistance of the conductor
The current flowing through the conductor
The time rate of change of magnetic field strength
The temperature of the conductor
The direction of the induced current in a conductor can be determined by:
Lenz's law
Ohm's law
Gauss's law
Ampere's law
A coil of wire is rapidly moved in and out of a magnetic field. The induced emf in the coil will be maximum when:
The coil is stationary
The coil is moving at a constant speed
The coil is moving into the magnetic field
The coil is moving out of the magnetic field
The phenomenon of electromagnetic induction is the basis for the operation of:
Electric motor
Electric generators
Transformers
All of the above
A magnetic field is changing at a rate of 0.02 T/s in a coil of wire with 200 turns. What is the induced emf in the coil?
The induced emf can be calculated using Faraday's law:
induced emf = -N x (ΔΦ/Δt)
where N is the number of turns, ΔΦ is the change in magnetic flux, and Δt is the change in time.
Given: N = 200 turns, ΔΦ/Δt = 0.02 T/s
induced emf = -200 x 0.02 = -4 V
A circular loop with a radius of 0.1 m is placed perpendicular to a magnetic field of 0.5 T. If the magnetic field collapses to zero in 0.1 seconds, what is the magnitude of the induced emf in the loop?
The magnitude of the induced emf can be calculated using Faraday's law:
induced emf = -N x (ΔΦ/Δt)
The change in magnetic flux can be calculated as ΔΦ = B x A, where B is the magnetic field and A is the area of the loop.
Given: r = 0.1 m, B = 0.5 T, Δt = 0.1 s
Area of the loop, A = π x r2 = 3.14 x (0.1)2 = 0.0314 m2
ΔΦ = B x A = 0.5 x 0.0314 = 0.0157 Wb
induced emf = -N x (ΔΦ/Δt) = -1 * (0.0157/0.1) = -0.157 V
A coil with 500 turns is exposed to a magnetic field of 0.02 T. If the magnetic field increases at a rate of 50 T/s, what is the magnitude of the induced emf in the coil?
The magnitude of the induced emf can be calculated using Faraday's law:
induced emf = -N x (ΔΦ/Δt)
The change in magnetic flux can be calculated as ΔΦ = B x A, where B is the magnetic field and A is the area of the coil.
Given: N = 500 turns, B = 0.02 T, Δt = 50 T/s
Area of the coil, A = (π x r2) = (π x (0.1)2) = 0.0314 m2
ΔΦ = B x A = 0.02 x 0.0314 = 0.000628 Wb
induced emf = -N x (ΔΦ/Δt) = -500 x (0.000628/50) = -0.00628 V
What is the main function of a transformer in an electrical circuit?
To regulate the voltage
To convert AC to DC
To store electrical energy
To generate electrical energy