Question

A student constructed a simple electric circuit where two light bulbs were connected in parallel. The circuit power source was a 6.0-V cell. One of the light bulbs had a resistance of 25 ohms, and the other had a resistance of 50 ohms. What was the combined resistance of the light bulbs in the circuit?

a) 75ohms

b) 42ohms

c) 25ohms

d) 17ohms

Answer 1

RT = 17 ohms

Step-by-step explanation:

For two parallel resistances in a circuit the combined resistance is given by:

`(1)/(R_T)=(1)/(R_1)+(1)/(R_2)\\\\(1)/(R_T)=(R_2+R_1)/(R_1R_2)\\\\R_T=(R_1R_2)/(R_1+R_2)`

R1 = 25 ohms

R2 = 50 ohms

You replace the values of R1 and R2 in the formula for RT:

`R_T=((25)(50))/(25+50)ohms=16.66\ ohms \approx 17\ ohms`

hence, the combined resitances is 17 ohms