Chapter 18, Problem 16Q

To determine

To explain:

Whether the current flowing in a resistor is completely used up or not.

Answer to Problem 16Q

Solution:

It is not the current which is used up because the rate of flow of charges cannot be reduced.

Explanation of Solution

Formula used:

• The current is defined as,

$I=\frac{q}{t}$

• The power loss in resistance (R) is given as

$P=I^{2}R=\frac{V^2}{R}$

Current is nothing but the rate of flow of charges and the charges flow in wire because of the potential difference offered by an external voltage source. From the negative terminal of the voltage source, electrons are repelled along the conducting wire, and through the positive terminal, the electrons are taken inside the voltage source. Thus, a chain of electrons is rotated through the conducting wire, resistor, and the voltage source. The driving force of this moving chain is the voltage source.

Now, the current is defined as the charge crossing any particular point in the path of this moving chain in a unit time. It is also clear that the number of electrons leaving the negative terminal of the voltage source will be equal to the number of electrons being received by the positive terminal of it. So, the rate of flow of charge entering the resistor will also be equal to the rate of flow of charge leaving the resistor.

Conclusion:

Hence, we can say that the current is not used up in a resistor but due to the flow of this current through the resistor, some phenomena like Joule-heating or emission of light can take place.