# Need of small charge in definition of electric field?

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1. Jan 20, 2015

### Raj Batra

Why do we need infinitesimally small charge in definition of electric field? Since the test charge cannot exert force on itself, F on test charge will not change whatever the value of test charge q is. So, F/q will be same for any value of test charge. Then why do we need this limit of infinitesimally small charge?

2. Jan 20, 2015

### Staff: Mentor

A larger charge will influence the charge distribution in the environment, and therefore the field at its position.