# NCERT Physics Class 12 Exemplar Ch 4 Moving Charges and Magnetism Part 7 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 28 A multirange current meter can be constructed by using a galvanometer circuit as shown in Fig. We want a current meter that can measure , and using a galvanometer of resistance and that produces maximum deflection for current of . Find that have to be used Value of Resistances

Solution:

For

For

And for

Gives

Q. 29 Five long wires , each carrying current are arranged to form edges of a pentagonal prism as shown in Fig. Each carries current out of the plane of paper. Magnetic Induction at Axis O

(a) What will be magnetic induction at a point on the axis ? Axis is at a distance from each wire.

(b) What will be the field if current in one of the wires (say ) is switched off?

(c) What if current in one of the wire (say) is reversed?

Solution:

1. Zero
2. Perpendicular to towards left.
3. Perpendicular to towards left.