Question

Two resistors 3 Ω and unknown resistor are connected in a series across a 12 V battery. If the

voltage drop across the unknown resistor is 6 V, find (a) potential across 3 Ω resistance (b) the

current through unknown resistor ‘R’ (c) equivalent resistance of the circuit

Answer 1

(a) total voltage =12V
voltage across 3ohm resistor=total voltage - voltage across unknown resistor
voltage across 3 ohm resistor =12-6=6 volts

first we need to find the unknown resistance-
assume the unknown resistance to be r
net resistance 3+r (series)
net current = v/r =12/3+r
ohm's law for unknown resistance
v=ir
6=(12/3+r)(r). ( both resistance have same current as they are in parallel)
6/r=12/3+r
6(3+r)=12r
18+6r=12r
18=6r
r=3 ohm
(b) current across unknown resistance (3 ohm now)
v=ir
6=I*3
i= 2 ampere
(c) equivalent resistance= R1+R2=3+3=6ohm
beacuse they are in series.

hope it helps!

Answer 2

Answer:

hope it help you

Explanation:

6=(12/3+r)(r). ( both resistance have same current as they are in parallel)

6/r=12/3+r

6(3+r)=12r

18+6r=12r

18=6r

r=3 ohm

(b) current across unknown resistance (3 ohm now)

v=ir

6=I*3

i= 2 ampere

(c) equivalent resistance= R1+R2=3+3=6ohm

beacuse they are in series.