Answer to Question #155915 in Electric Circuits for Jerick

Question

Supposed the battery in the figure is 45 V and the resistor R1 = 300 ohms. (a) What must the resistor R2 be in order that the current I be 0.45 A? (b) What are the currents I1 and I2?

Answer 1

Answer

a) Let unknown resistance is R₁

These resistances are in parallel so equivalent resistance

R'=$\frac{300R_1}{300+R_1}$ ...... Eq1

Using ohm"s law

V=IR'......... Eq2

Using eq 1 and 2 ad puting V=45V, I=0.45A

Then R found as

R=150 ohms

b) now currents

$I_1=\frac{V}{R_1}=\frac{45}{150}=0.3A$

$I_2=\frac{V}{R_2}=\frac{45}{300}=0.15A$