Question

Imagine making a copper to wear on your finger and attaching the ring to a 9-volt battery. Using the resitivity of copper, calculate the magnetic field at the centre of the ring.

You can assume some numbers to answer the question

Answer 1

Let radius of copper ring R = 5 cm = 0.05 m

cross section diameter of copper ring d= 0.5 mm = 0.0005 m

Resistivity of copper is given as = 1.7 x 10^-8 m

Now, Circumference or lengh of copper ring L= 2 x pi x R = 2x 3.14 x 0.05 = 0.314 m

Crosss sectional area A= d²/4 = 0.0005² /4 = 1.96 x 10^-7 m²

Resistance of a mterial is given by

So, current in the ring = V/Re = 9/0.027 = 333.33 A

Now, Magnetic field at center of a circular current is given by