Question

eshow 3 resistance of 1 ohm ,3 ohm,4 ohm connected to a cell of e.m.f. 2v and internal resistance 2.0 ohm . a. calculate the total resistance of the circuit. b. what reading will be shown by the ammeter. c. what reading will be shown by the ammeter if a similar cell is connected in series with the given cell ?​

Answer 1

Since figure is not given assuming resistances to be arranged in parallel manner in first case

Equivalent resistance by 3 external resistors

$\frac{1}{R_{p}} =\frac{1}{R_{1}} +\frac{1}{R_{2}} +\frac{1}{R_{3}} \\\\\frac{1}{R_{P}}=\frac{1}{1} +\frac{1}{3}+\frac{1}{4} \\\\\frac{1}{R_{P}}=\frac{12+4+3}{12}\\\\\frac{1}{R_{P}}=\frac{19}{12} \\\\R_{P}=\frac{12}{19}$

Also

ε=I(R+r)

Where

ε is EMF of cell

I is current

R is external resistance

r is internal resistance

substituting the values

we get

2=I($\frac{12}{19}+2)$

2=I($\frac{12+38}{19}$)

38=I(50)

I=$\frac{38}{50}$

For 2nd part you can just simply calculate the equivalent resistance in series and substitute in formula again TO GET THE ANSWER