Magnetism Flashcards
(24 cards)
What are the two types of magnetic poles?
North (N) and South (S).
What happens when two like poles are brought together?
They repel each other.
What happens when opposite poles are brought together?
They attract each other.
What are the differences between permanent and induced magnets?
Permanent magnets always produce a magnetic field. Induced magnets are materials that become magnetic when placed in a field.
Give three examples of magnetic materials.
Iron, Nickel, and Cobalt.
What do magnetic field lines show?
The direction of the magnetic force (always North → South). The strength of the field (closer lines = stronger field).
How can a magnetic field be visualized?
Using iron filings or a plotting compass.
Why does a compass needle point north?
Because the Earth has a magnetic field, and its magnetic South Pole is near the geographic North Pole.
What does this suggest about the Earth’s core?
The Earth’s core is magnetic and behaves like a giant bar magnet.
How does an electric current create a magnetic field?
A current-carrying wire produces a circular magnetic field around it.
How can the direction of the magnetic field be determined?
Using the Right-Hand Grip Rule: Thumb → Current direction, Fingers → Magnetic field direction.
What is a solenoid?
A coil of wire that produces a stronger, uniform magnetic field when carrying a current.
How can the strength of a solenoid be increased?
Increasing the number of coils. Increasing the current. Adding a soft iron core (creates an electromagnet).
What is the motor effect?
A current-carrying wire in a magnetic field experiences a force.
What is Fleming’s Left-Hand Rule?
Used to determine the direction of force in the motor effect. Thumb → Force (Motion), First Finger → Field (North to South), Second Finger → Current (Conventional, + to -).
How can the force on a conductor in a magnetic field be increased?
Increasing the current. Increasing the magnetic field strength (flux density, B).
What is the equation for force on a conductor in a magnetic field?
F = BIL
Where: F = Force (N), B = Magnetic flux density (T), I = Current (A), L = Length of conductor (m).
How does an electric motor work?
A coil of wire is placed in a magnetic field. The current in the coil produces a force on each side due to the motor effect. This causes rotation. A split-ring commutator ensures continuous rotation in one direction.
What is electromagnetic induction?
A potential difference (voltage) is induced across a conductor when it cuts through a magnetic field.
What are two ways to induce a current in a wire?
Moving a wire through a magnetic field. Changing the magnetic field around a stationary wire.
What does increasing the speed of movement do to the induced voltage?
Increases the voltage and current.
How does a transformer work?
An alternating current (AC) in the primary coil creates a changing magnetic field. This induces a voltage in the secondary coil.
What is the transformer equation?
Vs/Vp = Ns/Np
Where: Vp = Primary voltage, Vs = Secondary voltage, Np = Number of turns on primary coil, Ns = Number of turns on secondary coil.
What are step-up and step-down transformers?
Step-Up Transformer → More turns on secondary coil → Increases voltage. Step-Down Transformer → Fewer turns on secondary coil → Decreases voltage.
