P4.2: Uses Of Magnetism Flashcards
What is a solenoid?
A wire coiled up into a spiral shape
Q: What is the motor effect?
A: When a current-carrying wire is in a magnetic field, it gets pushed.
Q: What 3 things must be at 90° to each other in the motor effect?
A: Current, magnetic field, and force.
Q: What happens if current and magnetic field are parallel?
A: No force – they cancel out.
Q: What increases the motor effect force?
A: Stronger current and stronger magnetic field.
Q: What direction gives the maximum force?
A: When current is at 90° to the magnetic field.
Q: What rule helps find the direction of force?
A: Fleming’s Left-Hand Rule.
Q: What do the fingers show in Fleming’s Left-Hand Rule?
Thumb = Force
Forefinger = Field (N → S)
Second finger = Current (+ to -)
Q: What’s the formula for force on a wire?
A: Force = Magnetic field × Current × Length
Q: What are the units for that formula?
Force = Newtons (N)
Magnetic field = Tesla (T)
Current = Amps (A)
Length = Metres (m)
Q: A 0.5 m wire has 2 A current in a 0.4 T field. What’s the force?
A: 0.4 × 2 × 0.5 = 0.4 N
Q: How does a simple electric motor spin?
A: Current makes one side of the coil go up, the other down – it spins.
Q: What keeps a motor turning after half a turn?
A:
Momentum
Split-ring commutator flips the current
Q: What does the split ring commutator do?
A: Flips the current every half turn to keep the motor spinning.
Q: How does a loudspeaker use the motor effect?
Current in coil creates a magnetic field
It pushes/pulls the cone
Cone moves air = sound waves
Q: What makes the loudspeaker cone vibrate?
A: The current changes direction again and again (AC).
Q: What turns electrical signals into sound waves?
A: A loudspeaker.
