Question T5D02
From subelement T5 - T5D
What formula is used to calculate voltage in a circuit?
Why is this correct?
The correct formula is E = I × R because voltage (E) equals current (I) multiplied by resistance (R). This is Ohm's Law, which states that voltage across a component equals the current flowing through it times its resistance. Options B, C, and D are incorrect because they use division, addition, or subtraction instead of multiplication. Only multiplication gives the proper relationship between these three electrical quantities.
Memory tip
Remember the circle diagram method: cover the value you want to find, and the remaining values show the operation. When you cover E (voltage), I and R are side by side, meaning multiply. This visual technique works for all Ohm's Law rearrangements and helps avoid formula confusion during the exam.
Learn more
Think of voltage as electrical pressure that 'pushes' current through resistance. Just as water pressure increases with both flow rate and pipe restriction, voltage increases proportionally with both current and resistance. In practical circuits, this relationship helps you calculate voltage drops across components like resistors in antenna tuners or determine supply voltage requirements for specific current draws in your station equipment.
Think about it
Why do you think voltage is calculated by multiplying current and resistance rather than adding or dividing them?