### Tut 2 Electric Fields

1. What is meant by a "resultant electric field"
combined effect of two or more elctric fields acting at the same point

2. A positive and a negative charge are placed a few centimeters apart. Is it possible for there to be a point in between them, where the resultant electric field could be zero? Explain.

3. Draw the resultant electric field pattern of two positive point charges placed near each other.

4. The electric field strength a distance of d from a source charge is E. What would be the electric field strength at a distance 4/3 d ?

5. Two point charges carrying charges +5Q and -Q respectively are situated on the X axis as shown.

In which region along the X axis is it possible for the magnitude of the resultant electric field of the two charges to be zero?
Region...
A. M only
B. N only
C. P only
D. M and P
E. N and O

6. Two point charges of magnitudes 40nC and 30nC are 8cm apart.
6.1. Calculate the magnitude of the combined electric field exactly halfway between the charges.
6.2. If the charges were 40nC and -30nC instead, what effect would this have had on the above value? Explain.

7. Consider point P which is 20cm to the right of B.

7.1. Calculate the electric field strength of A only at position P.
7.2. Calculate the electric field strength of B only at position P.
7.3. Calculate the resultant electric field strength at P.

8. The resultant electric field at point P is zero.

8.1. Calculate the electric field strength of B at P.
8.2. State the electric field strength of A at P
8.3. What is the sign of charge A. Explain.
8.4. Calculate charge A, i.e. the value of Q.

9. Two charged particles are placed 200mm apart at points A and B as shown. X is a point midway between A and B. The charge at A is unknown while the charge at B is 2nC. The resultant electric field at X due to the presence of both charges is 5400 NC-1 due west.

What is the magnitude and sign of the charge at A?

10. Two charged objects, A and B are placed a distance of 0,02m apart. Their charges are 8uC and -2uC respectively.

10.1. Draw the combined electric field pattern for these two charges.
10.2. State Coulomb's law in words.
10.3. Calculate the magnitude of the electrostatic force that exists between the charges.
10.4. Calculate the electrostatic potential energy as a result of these charges.
10.5. P is a point 0,01m on the right of B.

Calculate the magnitude and direction of the resultant electric field at point P.