Two straight wires and are made of the same metal and have the same length

PHYSICS · Multi-part · A Level · Physics · Electricity · Electricity

Problem

Two straight wires

P

and

Q

are made of the same metal and have the same length. The radius of

P

0.6\,\text{mm}

while that of

Q

0.3\,\text{mm}

. Each wire carries a steady current of

5\,\text{A}

for

5\,\text{min}

. (a) Calculate the ratio of the electrical resistance of

Q

to that of

P

. (b) Find the ratio of the heat produced in

Q

to that in

P

during the given time. (c) Which of the two wires would be more suitable for use as a fuse in a

5\,\text{A}

household circuit? Give a reason based on your calculation.