Question

Two 24-ohm resistors are in parallel, and a 42-ohm resistor is in series with the combination. When 78V is applied to the three resistors, the voltage drop across the 42-ohm resistor is about
a. 49.8V
b. 55.8V
c. 60.7V
d. 65.3V

Answer 1

Answer:

c. 60.7 V

Explanation:

Two 24-ohm resistors are in parallel. Since the resistors are connected in parallel, The equivalent resistance in parallel can be calculated by :

1/Req = 1/R1 + 1/R2

1/Req = 1/24 + 1/24

1/Req = 2/24

1/Req = 1/12

Req = 12 ohm

Total equivalent resistance = 12 ohms + 42 ohm

= 54 ohm

Now 78V is applied to the three resistors. Using the ohm's law we can calculate the otal current flowing through the circuit:

I = V/R

= 78 / 54

= 1.44 A

Now the voltage drop across the 42-ohm resistor:

V = IR

= 1.44 × 42

= 60.7 V

Hence, the voltage drop across the 42-ohm resistor is 60.7 V.