FIGURE $Q32.1$shows emf phasors a, b, and c.

a. For each, what is the instantaneous value of the emf?

b. At this instant, is the magnitude of each emf increasing, decreasing, or holding constant?

We need to find instantaneous values of the emf in different position and explain is it increasing, decreasing or remain constant

As we know that the general expression of instantaneous emf is$V=V_o\cos (\omega t+\varphi )$

Due to the phase angle, the instantaneous emf changes from the x-axis. So, to find the emf for each phasor, we take the

projection of each phasor on x axis.

we can consider each block equals $20V$,

For phasor (a): The projection on x-axis is at$(-100V)$. so for phasor, the

number of blocks is $5$, therefore, the emf is

$EM{F}_a=-100V$

For phasor (b): The projection on x-axis is at $(+60V)$So for phasor, the

number of blocks is $3$, therefore, the emf is$5x20V=60V.$

$EM{F}_b=60V$

For phasor (c): The projection on x-axis is at $(+80V)$. so for phasor, the

number of blocks is $4$, therefore, the emf is $4x20V=80V$.

$EM{F}_c=80V$

We have given that the figure

We need to find that EMF at different position is increasing, decreasing or remain constant

a: The EMF a$(=-100V)$is Decreasing.

b: The EMF b$(=60V)$is Decreasing.

c: The EMF c$(=80V)$is Increasing.