Electromagnetism Flashcards
(34 cards)
What is a magnetic field?
A region around a magnetic material or a current-carrying conductor where magnetic forces act.
Magnetic fields are represented by field lines, which indicate strength and direction.
How are magnetic field lines represented?
Lines closer together indicate a stronger magnetic field and point from north to south outside a magnet.
What is the Earth’s magnetic field similar to?
Acts like a giant bar magnet, with its magnetic south near the geographic north.
Describe the magnetic field around a straight wire.
Field lines are concentric circles around the wire, with direction determined by the Right-Hand Thumb Rule.
What is the Right-Hand Thumb Rule?
Thumb points in the direction of current, fingers curl in the direction of the magnetic field.
What is the magnetic field inside a solenoid?
Strong and uniform, acting like a bar magnet with poles depending on the direction of current.
What is an electromagnet?
A temporary magnet created by passing a current through a coil of wire around a magnetic material.
List some uses of electromagnets.
- Electric bells
- Relays
- MRI machines
What factors affect the strength of an electromagnet?
- Number of Turns: More turns = stronger field
- Current: Higher current = stronger field
- Core Material: Soft iron core enhances magnetic field strength.
What is the motor effect?
A force experienced by a current-carrying conductor in a magnetic field.
How is the direction of force in the motor effect determined?
Using Fleming’s Left-Hand Rule.
What does Fleming’s Left-Hand Rule indicate?
- Thumb: Direction of Force
- First Finger: Direction of Magnetic Field (North to South)
- Second Finger: Direction of Current (Positive to Negative)
What is electromagnetic induction?
Generation of an electromotive force (EMF) or current in a conductor when it experiences a change in magnetic field.
What does Lenz’s Law state?
The induced current flows in a direction that opposes the change causing it.
What is Faraday’s Law of Induction?
EMF induced is proportional to the rate of change of magnetic flux.
How can induced EMF be increased?
- Increase the speed of relative motion between the conductor and the field
- Increase the strength of the magnetic field
- Increase the number of turns in the coil
What is a transformer?
Devices that change the voltage of an AC supply using electromagnetic induction.
What is a step-down transformer?
Decreases voltage, with more turns in the primary coil than secondary.
What is a step-up transformer?
Increases voltage, with fewer turns in the primary coil than secondary.
What is the efficiency of transformers?
Ideally 100%, but some energy is lost as heat.
What is the transformer formula?
$Vp/Vs = Np/Ns$ where:
* Vp, Vs = Primary and Secondary Voltages
* Np, Ns = Number of turns in Primary and Secondary coils.
What are applications of electromagnetism?
- Electric Motors
- Generators
- Transformers
- Induction Cooktops
- MRI Scanners
- Doorbells
What is the Right-Hand Thumb Rule used for?
Determining magnetic field direction around a current.
What is Fleming’s Left-Hand Rule used for?
Determining force direction in the motor effect.
