Which formula is used to determine power consumption in a DC circuit?

Which formula is used to determine power consumption in a DC circuit?

• A. P = V × I.
• B. P = V / I.
• C. P = I × E
• D. P = I + V

Answer: (C)

Power in a DC circuit is the rate at which energy is transfered, and it comes from multiplying the voltage across an element by the current through it: P = VI. If the symbol E is used to denote electromotive force (the source’s voltage), then P = I × E expresses the same relationship with a different symbol for voltage, so it correctly yields power in watts. The other forms don’t represent power: dividing voltage by current would give resistance, not power, and adding current and voltage mixes quantities that don’t combine to give power.

Power in a DC circuit is the rate at which energy is transfered, and it comes from multiplying the voltage across an element by the current through it: P = VI. If the symbol E is used to denote electromotive force (the source’s voltage), then P = I × E expresses the same relationship with a different symbol for voltage, so it correctly yields power in watts. The other forms don’t represent power: dividing voltage by current would give resistance, not power, and adding current and voltage mixes quantities that don’t combine to give power.