Question

assuming a current is flowing, what increases the strength of the magnetic field of a coiled electrical wire?
straightening the wire
changing the direction of the current flow
adding more coils to the wire
stopping the current

Explanation:

• Straightening the wire would reduce the magnetic field strength as the coiled shape (solenoid - like) concentrates the field; so this is incorrect.
• Changing the direction of current flow only changes the direction of the magnetic field, not its strength; so this is incorrect.
• Adding more coils (increasing the number of turns) in a coiled wire (solenoid) increases the magnetic field strength (since \( B \propto n \) where \( n \) is the number of turns per unit length for a solenoid - like structure with current \( I \)); so this is correct.
• Stopping the current would make the magnetic field zero, not increase it; so this is incorrect.

Answer:

C. adding more coils to the wire