Answer:
2. electromagnets can be made stronger by adding more coils to the solenoid.
3. electromagnets can be made stronger by increasing the strength of the electrical source.
Step-by-step explanation:
Electromagnets are not permanent, they act as magnets when current runs through its coils. They can be stronger by increase the current that goes through the coil surrounding them,. This can be done two ways: 1) increasing the actual current intensity, or 2) increasing the number of coils that wrap around them.