# Worksheet: Electromagnetic Induction in Generators

In this worksheet, we will practice describing electromagnetic induction in devices such as generators and dynamos.

Q1:

The graph shows the potential difference against time for three current sources. Which source provides rectified alternating current?

• A(c)
• B(b)
• C(a)

Which source provides direct current?

• A(b)
• B(a)
• C(c)

Q2:

The diagram shows four graphs of potential difference against time.    What type of current is produced by these four varying potential differences?

• AAlternating current
• BPulsating current
• CRectified alternating current
• DDirect current

Which graph shows a varying potential difference with the greatest frequency?

• A(d)
• B(a)
• C(b)
• D(c)

What is the peak voltage of graph (c)?

Which graph shows the varying potential difference with the lowest frequency?

• A(a)
• B(d)
• C(c)
• D(b)

What is the peak voltage of graph (d)?

Q3:

The graph shows the potential difference against time for three current sources. Which two current sources have a potential difference with a magnitude that is always nonnegative?

• A(b) and (c)
• B(a) and (b)
• C(a) and (c)

Which current source has a potential difference that is constant over time?

• A(a)
• B(b)
• C(c)

What is the peak voltage of source (c)?

What is the peak voltage of source (b)?

Which of the current sources shown in the graph is most likely to be produced by a dynamo containing a commutator?

• A(b)
• B(a)
• C(c)

Q4:

Parts (a), (b), (c), and (d) of diagram (A) show a setup for a simple alternating current generator. A single loop of copper wire rotates in a uniform magnetic field provided by two permanent magnets. The four parts of the diagram show the loop in four different positions as it rotates.

Diagram (B) is a graph of the current outputted by this generator over time. Which position of the loop in diagram (A) does the point in diagram (B) correspond to?

• A(d)
• B(b)
• C(a)
• D(c)

Which position of the loop in diagram (A) does the point in diagram (B) correspond to?

• A(c)
• B(a)
• C(b)
• D(d)

Q5:

The diagram shows the setup for a simple alternating current generator. A loop of copper wire spins about an axis in a uniform magnetic field between two permanent magnets. What components are marked by A in the diagram?

• ACarbon brushes
• BPermanent magnets
• CSplit-ring commutators
• DSolenoids
• ESlip rings

What components are marked by B in the diagram?

• ASplit-ring commutators
• BPermanent magnets
• CCarbon brushes
• DSlip rings
• EElectrodes

Q6:

Diagram (a) shows a generator consisting of a loop of wire that spins in the uniform magnetic field created between two permanent magnets. Diagram (b) shows a cross section of the generator, showing the direction of the magnetic field and the path of the two sides of the wire loop. Diagram (c) shows the potential difference induced in the wire by this motion against time. Which point on the graph in diagram (c) corresponds to the position of the wire shown in diagram (b)?   • AQ
• BP
• CS
• DR

Q7:

The diagram shows two designs of generators. Both designs use fixed permanent magnets to create a magnetic field and slip rings to conduct the induced current to an external circuit. Design (a) has a single loop of wire in the magnetic field, whereas design (b) has 5 loops. What is the advantage of design (b) over design (a)?  • ADesign (b) is cheaper to produce than design (a).
• BDesign (b) produces a higher frequency output voltage than design (a).
• CDesign (b) produces a lower output voltage than design (a).
• DDesign (b) produces a higher output voltage than design (a).
• EDesign (b) produces a lower frequency output voltage than design (a).

Q8:

The diagram shows two designs of generators.

Design (A) consists of two fixed permanent magnets that create a uniform magnetic field. A coil of wire rotates in the magnetic field, which induces a potential difference in the wire. Slip rings and carbon brushes are used to conduct the induced current to an external circuit.

Design (B) consists of two permanent magnets attached to a nonmagnetic disc. The two permanent magnets create a uniform magnetic field between them. The coil of wire within the magnetic field is fixed. Instead, the disc that the magnets are attached to rotates, and the magnets rotate around the coil of wire.

What is the advantage of design (B) over design (A)?  • ADesign (B) produces a higher frequency output voltage than design (A).
• BDesign (B) generates direct current, which is more useful than alternating current.
• CDesign (B) produces a higher output voltage than design (A).
• DDesign (B) does not use slip rings and carbon brushes. Carbon brushes wear out over time and have to be replaced. No component in design (B) has to be replaced.
• EDesign (B) is cheaper to manufacture than design (A) because slip rings are expensive.

Q9:

The diagram shows two designs for simple generators. The first design uses slip rings to conduct the induced current to an external circuit. The second design uses a commutator to conduct the induced current to an external circuit.  The graph below shows the potential difference against time for four different sources. Which line on the graph corresponds to the potential difference produced by the commutator design generator?

• A
• B
• C
• D

Which line on the graph corresponds to the potential difference produced by the slip-ring design generator?

• A
• B
• C
• D

Q10:

The diagram shows a design for a generator. A coil of wire spins in the uniform magnetic field created by two permanent magnets. What is the name given to the component marked A in the diagram? • AA permanent magnet
• BA slip ring
• CA commutator
• DA carbon brush
• EA solenoid