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An alternating voltage given by [tex][tex]$e = 140 \sin 3142 t$[/tex][/tex] is connected across a pure resistor of [tex][tex]$50 \Omega$[/tex][/tex].

Find:
(i) The frequency of the source.
(ii) The rms current through the resistor.

Sagot :

Alright, let’s solve the problem step-by-step.

### Given:
- The voltage equation: [tex]\( e = 140 \sin 3142t \)[/tex]
- A pure resistor [tex]\( R = 50 \, \Omega \)[/tex]

### Part (i): Finding the frequency of the source

We start with the given equation for the voltage:
[tex]\[ e = 140 \sin 3142t \][/tex]

The general form of an alternating voltage is given by:
[tex]\[ e = E_{\text{max}} \sin(2 \pi f t) \][/tex]

In this form, [tex]\( E_{\text{max}} \)[/tex] is the maximum voltage, and [tex]\( 2 \pi f \)[/tex] is the angular frequency.

We compare the given equation [tex]\( e = 140 \sin 3142t \)[/tex] to the general form [tex]\( e = E_{\text{max}} \sin(2 \pi f t) \)[/tex]:
- [tex]\( 2 \pi f \)[/tex] corresponds to [tex]\( 3142 \)[/tex]

From this, we can solve for [tex]\( f \)[/tex] (the frequency):
[tex]\[ 2 \pi f = 3142 \][/tex]
[tex]\[ f = \frac{3142}{2 \pi} \][/tex]

Using the numerical result we have:
[tex]\[ f \approx 500.0648311947352 \, \text{Hz} \][/tex]

So, the frequency of the source is approximately [tex]\( 500.065 \, \text{Hz} \)[/tex].

### Part (ii): Finding the RMS current through the resistor

First, we need to find the RMS (Root Mean Square) value of the voltage. For a sinusoidal voltage, the RMS value is given by:
[tex]\[ E_{\text{rms}} = \frac{E_{\text{max}}}{\sqrt{2}} \][/tex]

Given:
- [tex]\( E_{\text{max}} = 140 \, \text{V} \)[/tex]

We calculate [tex]\( E_{\text{rms}} \)[/tex]:
[tex]\[ E_{\text{rms}} = \frac{140}{\sqrt{2}} \][/tex]

Using the numerical result we have:
[tex]\[ E_{\text{rms}} \approx 98.99494936611664 \, \text{V} \][/tex]

Next, we need to find the RMS current through the resistor. Ohm's law states:
[tex]\[ I_{\text{rms}} = \frac{E_{\text{rms}}}{R} \][/tex]

Given:
- [tex]\( E_{\text{rms}} \approx 98.99494936611664 \, \text{V} \)[/tex]
- [tex]\( R = 50 \, \Omega \)[/tex]

We calculate [tex]\( I_{\text{rms}} \)[/tex]:
[tex]\[ I_{\text{rms}} = \frac{98.99494936611664}{50} \][/tex]

Using the numerical result we have:
[tex]\[ I_{\text{rms}} \approx 1.979898987322333 \, \text{A} \][/tex]

So, the RMS current through the resistor is approximately [tex]\( 1.98 \, \text{A} \)[/tex].

### Summary
(i) The frequency of the source is approximately [tex]\( 500.065 \, \text{Hz} \)[/tex].

(ii) The RMS current through the resistor is approximately [tex]\( 1.98 \, \text{A} \)[/tex].