opic 11.2 – Power generation and transmission – AHL Formative Assessment
NAME: _________________________________ TEAM:__
THIS IS A PRACTICE ASSESSMENT. Show formulas, substitutions, answers (in spaces provided) and units!
A rectangular coil of wire having dimensions 4.5 cm by 6.8 cm has 135 turns. It is rotating at a frequency
of 60 Hz in a magnetic field having a strength of 2.5 T.
1. What is its peak voltage e0? 1. 389.3 v
e0 = 2pfNBA
= 2p601352.5(0.0450.068)
= 389.3 v
2. Write the equation of the time dependence of its emf. 2. 389.3 sin 377t
e = e0 sin 2pft
= 389.3 sin (2p60t)
= 389.3 sin 377t
3. If the frequency is decreased to 40 Hz, what is this generator’s peak voltage?
3. 259.6 v
e0 = 2pfNBA
= 2p401352.5(0.0450.068)
= 259.6 v
The graphs of voltage and current for an ac circuit containing a resistor are shown.
4. Find the rms voltage corresponding to the
induced emf whose graph is shown.
4. 14.14 v
Vrms = V0 /  2
= 20 /  2
= 14.14 v
5. Find the peak voltage. 5. 20 v
6. Find the angular frequency of the coil that is
producing this emf. 6. 628.3 rad/s
 = 2pf
= 2p / T
= 2p/(1010-3)
= 628.3 rad/s
7. Find the maximum flux linkage of the coil that
is producing this emf. 7. 0.032 wb
e0 = 2pfNBA
NBA = e0 /2pf
= e0 /2p(1/T)
= 2010-3/2p
= 0.00318 wb
t / ms
I / A
2 1 0
-1
-2
5
10 20
15
t / ms
em f / V
0
10
20
-20
-40
5
10 20
1