Chapter 16, Problem 15Q

To determine

Why the test charges we use when measuring electric fields must be small.

Answer to Problem 15Q

Solution:

To measure electric field, we must use small test charges because it will not change the value of required electric field.

Explanation of Solution

The test charge has its own electric field. It can attract or repel the charges whose electric field is to be measured. So, if the magnitude of test charge is too large, it will change the value of electric field to be measured.

Also, while measuring the required electric field, it includes the electric field due to test charge also. If magnitude of test charge is too big, there will be a great variation between The measured value and the actual value of required electric field. This difference can be neglected if test charge is too small.