AQA A-level Physics - Internal resistance question

A resistor of resistance R and three identical cells of emf E and internal resistance r are connected as shown.
[*I will add the diagram in a reply below this*]

What is the current in the resistor?

A 3E/ (3R + r)
B 9E/ (3R + r)
C E/R
D 3E/R

pls explain how to solve this question, ty. 😁

Reply 1

kanji13

this is diagram of the circuit in the question

Reply 2

Eimmanuel

Study Forum Helper

Original post

by kanji13

Original post

by kanji13

this is diagram of the circuit in the question

When 3 cells of the same emf E are connected in parallel, the total effective emf of the combined cells is still E.
While the effective internal resistance of the 3 internal resistances r is
$\dfrac{1}{r_{\text{eff}}} = \dfrac{1}{r} + \dfrac{1}{r} + \dfrac{1}{r}$

The total resistance of the circuit becomes
$R + \frac{r}{3}$

Then apply “Ohm’s law” to find the current.
I will leave this step for you to fill in.