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billnye2010 · Apr 13, 2010, 07:06 PM

Physics Gr.12: Two resistors of 5 ohms and 9 ohms are connected in parallel. A 4 ohms resistor is then connected in series with the parallel combination. A 6 Volt battery is then connected to the series-parallel combination. What is the current through the 4 ohms resistor?

KISS · Apr 13, 2010, 10:50 PM

Can you compute this value?
What do you get?:

$R_{\text{}eq}$ = 5 Ω || 9 Ω + 4 Ω

The "||" is taken to mean "in parallel with"

Once you have Req, you can then compute the current which is I=6V/Req

Does this make any sense to you?

Unknown008 · Apr 18, 2010, 10:08 AM

Hmm... The way I was taught:

Find first the total resistance in the circuit.

To do that, you need to find the total resistance of the resistors in parallel first.

So, use the formula:

$\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2}$

When you got that, find the total resistance of the whole circuit.

This is done by using

$R_{total} = R_{resistance\ of\ resistors\ in\ parallel} + R_{last\ resistor}$

Using V = IR, you can find the current through the 4 resistor.