Question

The Potential Difference between the ends of a wire of resistance $5\Omega$, if 720 C of charge passes through it per minute.
A) 20 v
B) 30 v
C) 60 v
D) 15 v

Answer 1

Since we are given with some quantities, like Resistance, charge and Time. So we need to remember the formula for current and also we need to remember OHM’s Law.
Current(I) is defined as Rate of change of charge(q) or Flow of charge per unit time(t). So, by this definition we know $I=\dfrac{q}{t}$

Complete Solution:
First, we need to write our Given quantities from the question.
We have $R=5\Omega$
Charge(q) = 720C
Time(t) = 60 Seconds (1 minute)

Now by using Charge and time we can find current by using the formula $I=\dfrac{q}{t}$
$I=\dfrac{720C}{60\sec .}$
By solving the above equation, we get $I=12A$(ampere)

We have been asked to find the Potential difference (V), so we know that ohm’s law states the relation between potential difference(V), Resistance(R) and Current (I).
Ohm’s law is V=IR

Applying Ohm’s law and putting the values of “I” and “R”, we get
$V=12A \times 5\Omega$
V= 60V (volts)

According to the Question, we have been asked to find out the Potential Difference between the ends of a wire of resistance $5\Omega$, and By ohm’s law we get V=60 volts.

Hence the required solution for this question is option (C), 60V(volt).

Note:
Please remember that we need to convert the time into seconds even if the time is given either in minutes or Hours. Always remember to write the units of each quantity. Whenever you are given a charge with respect to time, always try to find the current first, and then proceed to the next quantity. After finding the current you can relate the given quantities with the Suitable Formula.