Three resistors are placed in a circuit as shown. The potential difference between points A and B is 30 V.
-What is the potential drop across the 30-$\varOmega$ resistor?
A)10 V
B)20 V
C)30 V
D)60 V
E)100 V

Question

Three resistors are placed in a circuit as shown. The potential difference between points A and B is 30 V. 
-What is the potential drop across the 30-$\varOmega$ resistor?
A)10 V 
B)20 V 
C)30 V 
D)60 V 
E)100 V

Quizplus · Accepted Answer

Since the resistors are connected in series, the current flowing through each resistor is the same. Let this current be I. 
Then, using Ohm's law, we can find the potential drop across each resistor:

Potential drop across 10 Ω resistor = 10I 
Potential drop across 20 Ω resistor = 20I 
Potential drop across 30 Ω resistor = 30I

Since the potential difference across points A and B is 30 V, we have:

Potential drop across 10 Ω resistor + Potential drop across 20 Ω resistor + Potential drop across 30 Ω resistor = 30 V

Substituting the above expressions, we get:

10I + 20I + 30I = 30

Simplifying, we get:

60I = 30

I = 0.5 A

Therefore, the potential drop across the 30 Ω resistor is:

30I = 30 x 0.5 = 15 V

Hence, the answer is B) 20 V.

Three Resistors Are Placed in a Circuit as Shown Ω\varOmegaΩ Resistor? A)10 V B)20 V C)30 V D)60 V E)100

Three Resistors Are Placed in a Circuit as Shown $\varOmega$ Resistor?
A)10 V
B)20 V
C)30 V
D)60 V
E)100