Answer:
B and D
Explanation:
The higher the voltage, the more current flowing and the better the magnetic field. Using a longer wire will result in more electric force around the nail, making it stronger.
The stronger electromagnet can be achieved using a high voltage than the actual.
Answer: Option B
Explanation:
The strength of the electromagnet depends upon the factors such as the current or voltage, then the number of coils present or the iron core. These all are directly influencing factors in respect to proportionality.
Out of the options given, using fewer coils will weaken the electromagnet. Using shorter nail will again weaken. Shorter wire would increase the strength. Therefore, the best suitable change is the use of higher voltage.
