Question

How much electrical energy is transferred per second by a 4V; 0.5A lamp?

• A. 20 J/S
• B. 2 J/S
• C. 6.8 J/S
• D. 4.8 J/S

Answer 1

The correct option is B 2 J/S

Answer is B.
Energy ($power\times time$) is measured in Joules and by including time (t) in the power formulae, the energy dissipated by a component or circuit can be calculated.
Energy dissipated = Pt or $VI\times tasP=VI$.
In this case, V = 4 V, I = 0.5 A and t = 1 second.
So, the electrical energy transferred is P = VI = 4 * 0.5 = 2 J/s.
Hence, the electrical energy is transferred per second by a 4 V and 0.5 A lamp is 2 J/s.