Answer:
if he wants to increase the strength of his electromagnet, he must increase the number of loops in the coil of wire along its length. If he uses an additional battery, the strength of his electromagnet will increase.
Step-by-step explanation:
The equation that relates the variables in interest is:
B = μ*N*I/L
B = strength of the magnetic field
n = number of loops in the coil of wire
I = current in the wire
μ = magnetic permeability
L = length of coil of wire
Then, if the number of loops increases, the strength of the electromagnet also increase.
An additional battery will cause an increment of the current in the wire , and therefore an increment of the strength of the electromagnet.