WorksheetsMotors, generators and AC
Total questions: 15
Worksheet time: 30mins
The direction of the induced current in the coil of a generator depends on the …
length of the coil.
speed of rotation of the coil.
direction of the magnetic field.
strength of the magnetic field.
Which ONE of the following combinations regarding the energy conversions in electric motors and electric generators is CORRECT?
ENERGY CONVERSION IN MOTORS: Mechanical to electrical
ENERGY CONVERSION IN GENERATORS: Electrical to mechanical
ENERGY CONVERSION IN MOTORS: Mechanical to electrical
ENERGY CONVERSION IN GENERATORS: Mechanical to electrical
ENERGY CONVERSION IN MOTORS: Electrical to mechanical
ENERGY CONVERSION IN GENERATORS: Electrical to mechanical
ENERGY CONVERSION IN MOTORS: Electrical to mechanical
ENERGY CONVERSION IN GENERATORS: Mechanical to electrical
Which ONE of the energy conversions below takes place when a DC motor is in operation?
Kinetic to electrical
Heat to mechanical
Mechanical to electrical
Electrical to mechanical
Which ONE of the following actions will NOT cause an increase in the induced emf in a coil if the coil is rotated in a uniform magnetic field?
Rotating the coil faster
Increasing the strength of the magnetic field
Increasing the number of turns of the coil
Replacing the coil with a coil of lower resistance
In a DC generator the current to the external circuit is delivered through the …
coils.
battery.
slip rings.
split rings (commutators).
The diagram above shows a current-carrying conductor lying in a uniform magnetic field directed to the right. The current flows into the page. Which ONE of the following arrows shows the direction of the force experienced by the conductor due to the magnetic field?
Some learners decided to build a small electrical generator in the laboratory. They then used this generator to investigate how the magnitude of the induced emf would change as the magnetic field strength changed.
Which ONE of the following is CORRECT regarding the variables for the investigation?
DEPENDENT VARIABLE: Magnitude of induced emf
INDEPENDENT VARIABLE: Number of turns of coil of generator
CONTROL VARIABLE: Magnetic field strength
DEPENDENT VARIABLE: Number of turns of coil of generator
INDEPENDENT VARIABLE: Magnitude of induced emf
CONTROL VARIABLE: Magnetic field strength
DEPENDENT VARIABLE: Magnitude of induced emf
INDEPENDENT VARIABLE: Magnetic field strength
CONTROL VARIABLE: Number of turns of coil of generator
DEPENDENT VARIABLE: Magnetic field strength
INDEPENDENT VARIABLE: Number of turns of coil of generator
CONTROL VARIABLE: Magnitude of induced emf
Which ONE of the following changes may lead to an increase in the emf of an AC generator without changing its frequency?
Decrease the resistance of the coil.
Increase the area of the coil.
Increase the resistance of the coil.
Decrease the speed of rotation.
The speed of rotation of the coils in an AC generator is increased. Which ONE of the following combinations of frequency and output voltage for the generator will occur as a result of the change?
FREQUENCY: Increases
OUTPUT VOLTAGE: Increases
FREQUENCY: No change
OUTPUT VOLTAGE: Increase
FREQUENCY: Decrease
OUTPUT VOLTAGE: Decrease
FREQUENCY: Increase
OUTPUT VOLTAGE: No change
A DC current passes through a rectangular wire loop OPQR placed between two pole pieces of a magnet, as shown above. Which TWO segments of the loop will experience an electromagnetic force when the loop is in the position above?
OP and PQ
QR and RO
OP and QR
RO and OP
The coils of an AC generator make one complete rotation. The resulting graph for the output emf is shown above. The position B on the graph is obtained when the plane of the coil is at an angle of … to the magnetic field.
0º
60º
90º
120º
In the sketch above, a conductor carrying conventional current, I, is placed in a magnetic field. Which ONE of the following best describes the direction of the magnetic force experienced by the conductor?
Parallel to the direction of the magnetic field
Opposite to the direction of the magnetic field
Into the page perpendicular to the direction of the magnetic field
Out of the page perpendicular to the direction of the magnetic field
A rectangular current-carrying coil, PQRS, is placed in a uniform magnetic field with its plane parallel to the field as shown above. The arrows indicate the direction of the conventional current. The coil will ...
rotate clockwise.
remain stationary.
rotate anticlockwise.
rotate clockwise and then anticlockwise.
Graph P represents the output emf of an AC generator. Graph Q is the output emf after a change has been made using the same generator. Which one of the following changes has been made to the generator to produce graph Q?
The number of turns of the coil has been doubled
The surface area of the coil has been doubled
The speed of rotation has been doubled
The strength of the magnetic field has been doubled
A DC generator operates at 80 Hz. The number of times the output voltage reaches a maximum in 1 second is ...
40
80
120
160
