The magnitude E of the electric field is called the electric field strength. The
ID: 1409499 • Letter: T
Question
The magnitude E of the electric field is called the electric field strength. The units of the electric field are N/C. A static charge changes the properties of the space that surrounds it, i.e. it sets up an electric field. The definition of electric field shows how we can map out the field: we can measure the force on a small positive test charge (probe charge) and determine magnitude and direction. Why do we need the test charge to be "small"? What does small mean? Why is the field pointing towards the negative charge? negative charge attracts the positive charge The field direction is defined by the direction of the moving positive charge.Explanation / Answer
(a) A test charge. means infinitesimal charge, which should not affect the charge distribution of the source. The electric field it produces does not redistribute charges on any conductors in our system. The test charge shouldn't exert force on itself. Thus, F/q will be same for any value of test charge.
(b) A negative charge placed in a field experiences a force towards it, and it moves charge. Field lines start on positive charges and end on negative charges, and the direction of the field line at a point tells you what direction the force experienced by a charge will be if the charge is placed at that point. If the charge is positive, it will experience a force in the same direction as the field; if it is negative the force will be opposite to the field.
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