Question

What will be the instantaneous voltage across the resistor after time 1/300 & when it's connected to 220V ,50hz AC

Answer 1

Answer:

Assuming that we have 50 Hz, 230V ac supply,(assuming resistive load, you'll have to consider some kind of load otherwise there'll be no current) the waveform of current will be simply attenuated by the value of Resistance, and there'll be no phase shift.

Now let's assume current I=2A(rms) and instantaneous value can be given by i= Im* sin(w*t). Since you want to find the instance at which the instantaneous value will become equal to rms value, we can put here I=2.

Solving the equation for theta(w*t) the exact instance can be found out. And if you want to find out in terms of time, then w can be replaced by 2*pi*f.

So, in general it can be said that the instance at which instantaneous value becomes equal to rms value can be given by theta= sin-1(rms value/Max value). And later on time can be found out by substituting w=2*pi*f.