30 Questions
What is the purpose of the cardboard with holes in the investigation of the field around a wire?
To spread the iron filings evenly on the surface
What happens to the direction of the magnetic field when the direction of the current in the wire is reversed?
The magnetic field direction reverses
What is the purpose of the variable resistor in the circuit used to investigate the field around a wire?
To control the current flowing through the wire
Which of the following is NOT used in the investigation of the field around a wire?
Solenoid
What is the purpose of tapping the cardboard slightly during the investigation?
To ensure the iron filings are evenly distributed
What is the role of the clamp stand in the investigation of the field around a wire?
To hold the wire in a vertical position
What type of component only allows current to flow in one direction?
Diode
Which device is used to measure potential difference in a circuit?
Voltmeter
In what configuration are ammeters connected in a circuit?
Series
Which component is used to protect expensive components from current surges?
Fuse
What type of components use electromagnetic effects?
Transformers
Which component is known for 'stepping up' or 'stepping down' current and potential difference?
Transformer
What equation is used to determine the combined resistance of any combination of two resistors?
$rac{1}{R} = rac{1}{R_1} + rac{1}{R_2}$
What is the relationship between the potential difference across each resistor in a potential divider circuit?
The potential difference across each resistor is proportional to its resistance.
If the resistance of one of the resistors in a potential divider circuit is increased, what happens to the potential difference across that resistor?
The potential difference across the resistor increases.
Which of the following is NOT a common, incorrect simplification made when determining the combined resistance of two resistors in parallel?
$R = R_1 - R_2$
What is the first step in calculating the combined resistance of two resistors in parallel?
Find the value of $rac{1}{R_1} + rac{1}{R_2}$.
What is the relationship between the potential difference across the two resistors in a potential divider circuit?
The potential difference across the resistors is directly proportional to their resistance.
What happens when the magnet is in position 3?
No EMF is induced in the coil
In what scenario does the coil have maximum induced EMF?
When the number of field lines cut is at its maximum
What does the alternator's A.C output lead to?
Current in both positive and negative regions of the graph
At what angle to the coil do magnetic field lines need to be for maximum induced EMF?
90°
What is the relation between the coil's plane and the field lines for induced EMF to be zero?
Parallel
How does a change in magnet pole orientation affect induced EMF?
It reverses the direction of induced EMF
What happens to the needle when the magnet is stationary?
There will be no deflection of the needle
According to Lenz's Law, the direction of the induced potential difference always:
Opposes the change that produces it
When a magnet is pushed into a coil of wire, the end of the coil closest to the magnet becomes a:
North pole
When a magnet is pulled away from a coil of wire, the end of the coil closest to the magnet becomes a:
South pole
What is the purpose of Lenz's Law?
To explain the direction of induced current
What is the main factor that determines whether a potential difference will be induced in the coil?
The relative movement between the coil and the magnetic field
Study Notes
Investigating Magnetic Fields
- Magnetic field patterns around straight wires and solenoids can be investigated using a thick wire, solenoid, cell, ammeter, variable resistor, and connecting wires.
- Iron filings or a compass can be used to observe the magnetic field around a wire.
- Reversing the current direction reverses the direction of the magnetic field.
Experiment 1: Plotting the Magnetic Field Around a Wire
- A thick wire is attached to a clamp stand and secured vertically to a cardboard.
- The wire is connected to a series circuit containing a variable resistor and ammeter.
- A plotting compass is used to determine the magnetic field around the wire.
Determining Resistance in Parallel
- The combined resistance of two resistors is calculated using the equation: 1/R = 1/R1 + 1/R2.
- The value of R is found by taking the reciprocal of the sum of the reciprocals of R1 and R2.
Potential Dividers
- A potential divider splits the potential difference of a power source between two components.
- The potential difference across each resistor depends on its resistance.
- The resistor with the largest resistance gets a greater share of the potential difference.
Power Supplies, Meters, and Electromagnetic Components
- Cells, batteries, power supplies, and generators supply current to a circuit.
- Resistors, meters (ammeters and voltmeters), and electromagnetic components (magnetising coils, relays, and transformers) are used in circuits.
- Fuses protect expensive components from current surges and act as a safety measure against fire.
Diodes
- Diodes allow current in one direction and are represented by a circuit symbol.
- Diodes can be connected to AC and DC sources.
Induced EMF and Magnetic Fields
- When a magnet is in position 3, the magnetic field lines do not cut the coil, and there is no induced EMF.
- When a magnet is in position 4, the magnetic field lines cut the coil, and there is a maximum induced EMF.
- The induced EMF relates to the number of field lines cut by the coil: when the coil is parallel to the field lines, induced EMF = 0; when the coil is perpendicular to the field lines, induced EMF is maximum.
Lenz's Law
- Lenz's Law states that the direction of an induced potential difference always opposes the change that produces it.
- The law is demonstrated by the force opposing the movement of a magnet or wire.
Exam Tip
- Remember how the induced EMF relates to the number of field lines cut by the coil.
Test your understanding of electromagnetic induction with this quiz question. Determine the correct outcome when a magnet is stationary near a coil according to Faraday's law. Choose the option that explains the deflection of the needle accurately.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
