What is the current in the circuit shown in the figure for t

What is the current in the circuit shown in the figure for the following? (Let R = 4 Ohm end V = 30 V. Calculate the total current drawn from the battery.) when the switch is open when the switch is closed

Solution

For any circuit with resistance R and potential difference V, the current is given as I = V/R

Also, for resistors connected in series the net resistance is given as: Rnet = R1 + R2 + R3 and so on. While for resistors connected in parallel, the net resistance is given as: 1/ Rnet = 1 / R1 + 1 / R2 + 1/R3 and so on.

We will make use of the above to solve the given problem:

Part a.) When the switch is open, the net resistance would be: Rnet = 2R = 8 ohms

And V = 30 Volts

That is, net current = V/R = 30 / 8 = 3.75 amperes.

Part b.) When the switch is closed, the net resistance would be given as:

Rnet = 5R/(5 + R) + 1R / (1+R) = 20/9 + 0.8 = 3.022 Ohms

And the potential difference = V = 30 Volts

So the net current drawn = V/R = 30 / 3.022 = 9.926 Amperes.