Question

Two blocks of copper with density of 100 kg/m^3 are twisted into wires of length 100 km and thickness 0.1mm. copper is a very ductile material. its ductility is measured in terms of percentage elongation upon application of tensile forces. the conductivity of the copper wire is extremely high rendering it useful in the construction of many electronic circuits. if the voltage through one such circuit is 18 v and the current flowing in the circuit is 190 ma. what is the resistance of the wire?.

Answer 1

As per ohm's law resistance of the wire is given by

$R = \frac{V}{I}$

here V = voltage difference across the ends of wire

I = current through the wire

now given here that

V = 18 volts

I = 190 mA = 0.190 A

now using the above values

$R = \frac{18}{0.190}$

$R = 94.74 ohm$

so the resistance of wire is 94.74 ohm

Answer 2

Resistance = V/I = 14/215 = 0.065 = 0.07(approx) (Simply NOT convert the current unit because they haven't mentioned any unit in their options & in other of the same kind of questions where they mention the unit in the options first do the "V/I" operation with whatever they have given in the question as it is, like first don't convert the "mA into A".

first do the "V/I" operation then convert the whole output into the appropriate unit by keeping an eye on the option's unit.)

Ans. (D) 0.07