A piece of wire length 30cm and cross sectional area of 0.5mm^2 has a resistance of 5ohms at 20°c. It is then heated to a temperature of 150°c. Calculate it's resistivity at 20°c

8.333*10^-6 ohms

Explanation:

Resistivity of a material is expressed as;

p = RA/l

R is the resistance of the material

A is the cross sectional area

l is the length of the material

Given

R = 5 ohms

A = 0.5mm^2

A = 5 * 10^-7m^2

l = 30cm  = 0.3m

Substitute into the formula;

p = (5 *  5 * 10^-7m^2)/0.3

p = 25 * 10^-7/0.3

p = 0.0000025/0.3

p = 8.333*10^-6

Hence its resistivity at 20 degrees Celsius is 8.333*10^-6 ohms

this is poiselle's equation from fluid mechanic in physics. mech eng

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min