EduNinjaThe diagram shows an a.c. generator.
The graph shows the potential difference (p.d.) between points X and Y plotted against time. A positive value of p.d. indicates that X is more positive than Y.
Which diagram shows the position of the coil at point P on the graph?
A simple a.c. generator has a coil rotating in a magnetic field.
What happens to the peak electromotive force (e.m.f.) and to the frequency of the a.c. output when the coil is rotated faster?
peak e.m.f.
frequency
greater
greater
greater
no change
no change
greater
no change
no change
The diagram shows a simple a.c. generator. The magnet rotates around a fixed coil wound round a fixed iron core. The electromotive force (e.m.f.) output is a sine wave, a series of crests, zeros and troughs.
The magnet is shown in three positions, P, Q and R, during its rotation. The magnetic field in the coil is zero at Q but changing most rapidly.
Which statement about the induced e.m.f. in the coil is correct?
The magnitude of the e.m.f. at position Q is larger than that at position P.
The magnitude of the e.m.f. at position Q is zero.
The magnitude of the e.m.f. at position Q is smaller than at position R, but not zero.
The magnitude of the e.m.f. at position R is larger than at position P.
Fig. 8.1 shows how the electromotive force (e.m.f.) of a 60 Hz alternating current (a.c.) power supply varies with time.
Fig. 8.1
Calculate the time period of the a.c.
time period =
Graph X shows the output from an a.c. generator.
Which changes can be made so that the generator produces graph Y ?
Decrease the magnetic field strength and decrease the speed of rotation only.
Increase the magnetic field strength and decrease the number of coils only.
Increase the number of coils only.
Increase the speed of rotation only.
In an a.c. generator, a coil is rotated in a magnetic field and an electromotive force (e.m.f.) is induced in the coil.
In which position of the coil does the e.m.f. have the largest value?
The diagram shows an a.c. generator used to power a lamp. The coil rotates in a clockwise direction.
Which magnetic poles are X and Y ?
X
Y
N pole
N pole
N pole
S pole
S pole
N pole
S pole
S pole
Fig. 6.1 shows two bar magnets.
Fig. 6.1
Fig. 6.2 shows the same bar magnets with a coil of wire between them.
Fig. 6.2
Name the parts labelled A in Fig. 6.2.
Explain how rotating the coil in Fig. 6.2 continuously causes the galvanometer needle to show an alternating current.
The diagram shows an electric generator with the coil in a vertical position.
Which row describes the generator?
the generator
produces
the voltage output
will be zero when
a.c.
the coil is horizontal
a.c.
the coil is vertical
d.c.
the coil is horizontal
d.c.
the coil is vertical
The diagram shows an a.c. generator.
As the coil passes through the position shown, the output voltage is +10 V .
When does the output voltage become -10 V ?
when the coil has turned through
when the coil has turned through
when the coil has turned through
when the coil has turned through