Electric fields

What is the unit of charge?

• Newton

• Joule

• Coulomb

• Farad

What is the direction of electric field at a given point?

• It has same direction as the force experienced by a negative charge at a given point.

• It has same direction as the force experienced by a positive charge at a given point.

• It depends on the sign of charge.

• It always points towards the center of the charge.

How do you define electric field?

What is the unit of electric field?

• C

• N/C

• C/N

• Cm

What is the equation for the electric field of a point charge?

Charge q1=7.00 μC is at the origin, and charge q2=-5.00μC is on the x - axis, 0.300 m from the origin.

(a) Find the magnitude and direction of the electric field at point P, which has coordinates (0, 0.400) m.

(b) Find the force on a charge of 2.00×10^(-8) C placed at P.

Four point charges of equal magnitude but difference signs are arranged on the corners of a square as shown left. Which of the vectors shown represents the direction of the net force acting on the charge at the upper left-hand corner of the square due to the other charges?

• A

• B

• C

• D

• 9/4

• 1/1

• 4/9

• 1/4

Which of the following statements must be true of the signs of the charges?

• only qA and qB have the same sign.

• only qA and qC have the same sign.

• only qB and qC have the same sign.

• Charges qB and qC have difference signs.

Which of the following is true about the sign of charge qA?

• The sign of qA must be same as qB.

• The sign of qA must be same as qC.

• The sign of qA must be same as either qB or qC, whichever has the greater magnitude.

• It is possible that qA could be either positive or negative.