What is the current through resistor R4 in the circuit?

• A. 9A
• B. 7A
• C. 3A
• D. 4A

Answer: (A)

Current through a resistor is set by the voltage across that resistor and its resistance, and the way the rest of the circuit routes current. To find I through R4, you first determine the voltage across it and then apply Ohm’s law: I = V across R4 divided by R4.

If R4 is in series with other elements, the same current flows through every component in that series path, so you compute the overall current from the source using the total series resistance. If R4 is in parallel with other branches, the voltage across R4 is the same as the voltage across the parallel network, and you calculate I through R4 as V across R4 divided by R4; with multiple parallel branches you may use current division to find how the total current splits, assigning a share to R4 based on the other branch resistances.

For mixed networks, you’d typically use nodal analysis or mesh analysis to find the voltages or loop currents, then apply I = V/R for R4.

The stated answer of 9 A means the voltage across R4 and its resistance combine to give 9 A via I = V/R. For example, if R4 were 1 Ω, that would require 9 V across R4. If you can share the circuit diagram or the values around R4, I can walk through the exact steps to confirm the current through R4.