To determine the polarity of the voltage drop across a resistor, it is necessary to know

The correct answer is option 2):(the direction of current through the resistor.)

Concept:

• The polarity of the voltage drop across any resistive component is determined by the direction of current flow through it: positive entering, and negative exiting.

• When using conventional current flow, we can trace the direction of the current in the same circuit by starting at the positive (+) terminal and going to the negative (-) terminal of the battery, the only source of voltage in the circuit. From this, we can see that the current is flowing clockwise, from point 1 to 2 to 3 to 4 to 5 to 6 and back to 1 again.

• As the current encounters the 5 Ω resistance, voltage is dropped across the resistor’s ends. The polarity of this voltage drop is positive (+) at point 3 with respect to point 4.

• We can mark the polarity of the resistor’s voltage drop with negative and positive symbols, in accordance with the direction of the current; whichever end of the resistor the current is entering is positive with respect to the end of the resistor it is exiting