Electromagnets are made out of a coil of wire (wire curled in series). This is more effective in producing a magnetic field than just a wire running straight. The magnetic field disappears when the current is turned off. MRI scan uses electromagnets. i. Magnetic strength of an electromagnet can be easily altered by: a) Changing current b) Increasing no. Of turns c) Both a and b d) Noneii. Advantage of electromagnet over bar magnet is: a) Polarity of electromagnet can be reversed b) Polarity of electromagnet cannot be reversed c) Being a temporary magnet d) None iii. One disadvantage of electromagnet over bar magnet is: a) Use of power b) Polarity reversal c) Both a and b d) None iv. Mobiles and telephones uses: a) Bar magnet b) Electromagnetc) Earth’s magnetism d) None v. Full form of MRI is: a) Magnetic resonance imaging b) Magnetic remanence intensity c) Magnetic resonance and interference d) None