Answer
(a) $45V$
(b) $40Hz$
(c) $40rps$
(d) $E(t)=31.8 cos(80\pi t)$
Work Step by Step
(a) The maximum voltage can be read from the oscilloscope as $V_{max}=45V$
(b) It can be found from the oscilloscope that within 0.1 second there were 4 periods,
which means that the frequency is $f=4/0.1=40Hz$
(c) The number of revolutions per second the armature in
the generator make is the same as the frequency which is $40rps$
(d) Use the formula $f=\frac{\omega}{2\pi}=40$, we have $\omega=80\pi$ and the cosine function
for the voltage variation is $E(t)=a\cdot cosin(\omega t)$. With $a=RMS=\frac{V_{max}}{\sqrt 2}=\frac{45}{\sqrt 2}=31.8V$, the function becomes $E(t)=31.8 cos(80\pi t)$ (assuming t=0, E(0)=31.8V)
