If the resistance doubles while the current remains constant, what happens to the emf E?

• A. E halves
• B. E remains the same
• C. E becomes zero
• D. E doubles

Answer: (D)

Ohm's law relates emf, current, and resistance through E = I R. If the current is held fixed, the emf scales directly with resistance. So when resistance doubles, the emf must also double to keep the same current. The other possibilities would violate E = I R under the given condition. Additionally, with the current unchanged, the power delivered (P = E I) would increase correspondingly as the emf increases.