Question

A copper wire of length 1 m and radius 1 mm is joined in series with an iron wire of length 2 m and radius 3 mm and a current is passed through the wires. The ratio of the current density in the copper and iron wires is​

Answer 1

Answer:

Correct option is

B

9:1

Current density, J=

A

I

where I= steady current and A= cross section of wire.

Here, J

1

=

A

1

I

=

πr

1

2

I

and J

2

=

A

2

I

=

πr

2

2

I

Thus,

J

2

J

1

=

r

1

2

r

2

2

=

1

2

3

2

=9:1

Answer 2

Answer:

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