When is the e.m.f. at its maximum value (peak or trough) — when the coil is horizontal or vertical?
When the coil is horizontal .
What happens to the magnetic field direction if the current is reversed?
The magnetic field direction reverses.
What is the main part that rotates in a simple a.c. generator?
A wire coil rotates in a magnetic field.
How can you find the direction of the magnetic field around a current-carrying wire?
By using the right-hand grip rule.
Which other factors can increase the induced e.m.f. apart from moving the conductor faster?
Use a stronger magnet or more turns in the coil. /
A transformer has 800 turns on the primary coil and 200 turns on the secondary coil. The input voltage is 240 V. Calculate the output voltage.
60V
A step-up transformer increases the voltage from 12 V to 240 V. If the secondary coil has 1000 turns, calculate the number of turns on the primary coil.
50 turns
What factors increase the strength of a solenoid’s magnetic field?
More turns of wire, larger current, and using an iron core.
Which law related to this statement "The direction of the induced e.m.f. always opposes the change that causes it" ?
Lenz’s Law
How can you increase the turning effect on a current-carrying coil?
By increasing the number of turns on the coil / increasing the current, / increasing the strength of the magnetic field.
What is the function of slip rings and brushes in an a.c. generator?
To allow current to flow out of the rotating coil while keeping the connections continuous.
According to Fleming’s Left-Hand Rule, what does each finger represent?
(Y)Thumb → Force (motion) , (Z)First finger → Magnetic field , (X)Second finger → Current
State one difference between a permanent magnet and an electromagnet.
A permanent magnet always has a magnetic field, while an electromagnet produces a magnetic field only when current flows through it.
A solenoid has 200 turns, carrying 3A of current. Suggest two ways to increase its magnetic field strength without changing the current.
Increase the number of turns of the solenoid and Insert a soft iron core.
An ideal transformer has a primary voltage of 230 V and supplies a current of 2 A. The secondary voltage is 115 V. Calculate the current in the secondary coil.
4A
How can you increase the induced e.m.f.?
Move the conductor or magnet faster.
What can be used to show the magnetic field pattern around a wire?
Iron filings or a plotting compass.
If a transformer has 200 turns on the primary coil, 50 turns on the secondary coil, and the primary voltage is 240 V, what is the secondary voltage?
60V
When is the e.m.f. zero?
When the coil is vertical .
What shape is the magnetic field around a straight wire carrying current?
Concentric circles around the wire.
What happens when a conductor moves across a magnetic field
An electromotive force (e.m.f.) is induced in the conductor.
What rule is used to determine the relative directions of force, field, and "induced current"?
Fleming’s Right-Hand Rule