MCAT Physics Question 83: Answer and Explanation

Question: 83

8. In the circuit below, what is the voltage drop across the resistor?

Correct Answer: C

Explanation:

To determine the voltage drop across the

resistor, start by calculating the total resistance in the circuit. For the resistors in parallel, the total resistance is

The total resistance in the circuit is the sum of the remaining resistor and the equivalent resistance of the other two:

Now that we know the equivalent resistance, we can calculate the total current using Ohm's law:

Finally, we can determine the voltage drop across the parallel resistors. The voltage drop across the

resistor must be

Therefore, there must be a 5 V drop across both the

resistor and 2 ? resistor, according to Kirchhoff's loop rule. Each of these resistors forms a complete loop in combination with the

resistor and 10 V voltage source, and the net potential difference around any closed loop must be 0 V.