Answer:

7) a. When using batteries, increasing the voltage also increases the current   in the circuit. ... As the number of devices placed within one series circuit increases, the resistance also increases. In a parallel circuit, as electrical devices are added the resistance decreases.

   b. The combined magnetic force of the magnetized wire coil and iron bar makes an electromagnet very strong. In fact, electromagnets are the strongest magnets made. An electromagnet is stronger if there are more turns in the coil of wire or there is more current flowing through it.

Explanation:

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