Question 1: A magnetic field is produced whenever:
- Electric current flows through a conductor
- A conductor sits at rest with no current flowing
- Two insulators touch each other
- Voltage is exactly zero
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BASIC
NEC 2023
Magnetism & Electromagnetic Induction Practice Test
Free online magnetism and electromagnetic induction practice test. 25 basic electrical questions on magnetic fields, electromagnets, Faraday's Law, Lenz's Law, and how induction powers generators and transformers. Good for electrician exam prep.
TOPICS COVERED
Magnetic Fields Basics
Right-Hand Rule
Magnetic Poles
Magnets vs Electromagnets
Magnetic Flux Unit
Flux Density Unit
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Almost every piece of electrical equipment — motors, generators, transformers, relays, solenoids — works because of magnetism. Current flowing through a conductor always creates a magnetic field around it (right-hand rule). Electromagnetic induction is the reverse: a CHANGING magnetic field induces a voltage in a nearby conductor (Faraday's Law). Lenz's Law says the induced current always opposes the change that created it. Know the difference between mutual induction (one coil inducing voltage in another — how a transformer works) and self-induction (a coil inducing voltage in itself — how an inductor works).
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38 min
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TimeMagnetism & Electromagnetic Induction Practice Test — Question List
Question 2: Using the right-hand rule for a straight current-carrying conductor, if your thumb points in the direction of current flow, your curled fingers show:
- The direction of the magnetic field circling the conductor
- The amount of resistance in the conductor
- The voltage drop across the conductor
- The temperature of the conductor
Question 3: Magnetic poles behave according to which basic rule?
- Like poles repel, unlike poles attract
- Like poles attract, unlike poles repel
- All poles always attract
- All poles always repel
Question 4: The main difference between a permanent magnet and an electromagnet is that an electromagnet:
- Only produces a magnetic field while current flows through it
- Is always stronger than a permanent magnet
- Cannot attract iron or steel
- Never has a north or south pole
Question 5: Magnetic flux, represented by the symbol Φ, is measured in which unit?
- Weber (Wb)
- Tesla (T)
- Henry (H)
- Ohm (Ω)
Question 6: Magnetic flux density, represented by the symbol B, is measured in which unit?
- Tesla (T)
- Weber (Wb)
- Farad (F)
- Volt (V)
Question 7: Permeability is a material property that describes:
- How easily a material allows magnetic flux to pass through it
- How much electrical resistance a material has
- How much heat a material can withstand
- How well a material conducts electric current
Question 8: Electromagnetic induction is the process of:
- Producing a voltage (EMF) in a conductor by changing the magnetic field around it
- Storing electric charge on two metal plates
- Converting AC to DC using diodes
- Reducing resistance in a conductor by cooling it
Question 9: According to Faraday's Law, the size of the induced EMF in a coil depends mainly on:
- The rate at which the magnetic flux through the coil is changing
- The color of the wire insulation
- The resistance of the coil wire only
- The ambient room temperature
Question 10: Lenz's Law states that the direction of an induced current will:
- Always oppose the change in magnetic flux that produced it
- Always match the direction of the source current exactly
- Have no relationship to the magnetic flux at all
- Always flow in the same direction as DC current
Question 11: Mutual induction — where a changing current in one coil induces a voltage in a separate, nearby coil — is the basic principle behind how a ___ works.
- Transformer
- Resistor
- Diode
- Fuse
Question 12: Self-induction occurs when:
- A coil's own changing current induces a voltage in itself, opposing the change
- Two separate coils exchange energy with each other
- A resistor heats up under load
- A capacitor discharges through a short circuit
Question 13: Eddy currents are:
- Small circulating currents induced within a conductive core by a changing magnetic field
- The main current flowing through a transformer's primary winding
- A type of current that only exists in DC circuits
- The current drawn by a load at unity power factor
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