Hello all,

I'm stuck on a couple of revision questions and was wondering if someone could help?

questions are:

1).A sinusoidal current has an average value of 7.5 Amps. Determine its r.m.s. value.
2).A sinusoidal waveform of 10 Volts r.m.s. passes through a voltage +5 Volts, 200 times in 2 seconds. Find its frequency.

Unfortunately I haven't been able to attempt these yet as I'm unsure which equations to use?

 

Lets take 2) first

Is the positive peak voltage greater than, equal to or less than +5 volts?
Can you calculate its actual value?

And what do you know about RMS and average current? Have you seen the integrals? Have you been told what form factor means?

 

Wouldn't the average of any sinusoid be zero?

How many times does a sinusoid pass any given voltage (less than its peak) per cycle?

 

Instead of looking for an equation to throw at the problem, try instead understanding the fundamental concepts.

What is the point of RMS measurements in the first place? What is it that they tell you?