Question

A 20.0 Ω, 15.0 Ω, and 7.00 Ω resistor are connected in parallel to an emf source. A current of 7.00 A is in the 15.0 Ω resistor. Calculate the equivalent resistance of the circuit. Answer in units of Ω.
What is the potential difference across the source?
Answer in units of V.
Calculate the current in the 20.0 Ω resistor. Answer in units of A.

Answer 1

PART A)

Equivalent resistance in parallel is given as

$\frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}$

now we have

$\frac{1}{R} = \frac{1}{20} + \frac{1}{15} + \frac{1}{7}$

$R = 3.85 ohm$

PART B)

since potential difference across all resistance will remain same as all are in parallel

so here we can use ohm's law

$V = iR$

As we know i = 7 A current flows through 15 ohm resistance

$V = (7 A)(15 ohm) = 105 volts$

PART C)

Similarly ohm's law for 20 ohm resistance we can say

$V = iR$

$105 = i(20 ohm)$

$i = 5.25 A$

Answer 2

Answer:

Equivalent Resistance = 3.85 ohm

Voltage is 105 volts

Current is 5.25 A

Explanation:

Part 1

Equivalent resistance in parallel is given as

1/Re = 1/R1 + 1/R2  + 1/R3

By putting the values

1/Re = 1/20 + 1/15 + 1/7

Equivalent Resistance = 3.85 ohm

Part 2 By Using Ohm Law

V = IR

Since i = 7  so

Voltage = (7 A)(15) =

V = 105 volts

Part 3

According to Ohms law

V = IR

105 = I (20)

I = 5.25 A