Revision MIDTERM
EXERCISE
Question 1
a) Two point of charges of opposite sign and same magnitude 3.5 μC are separated by a distance of 5 cm. Find (i) the magnitude and direction of the electric field strength, E at the midpoint between the charges. (ii) the magnitude and direction of the force F on an electron placed at the midpoint. Answer: i) E net = 1.008x108 N/C toward the –ve charge ii) F net = 1.6128x10-11 N toward +ve charge
Question 2
a) Based on Figure 1 above, the values for Q1, Q2 and Q3 are -86 μC, +50 μC and +65 μC respectively.
(i) Calculate the net electrostatic force on charge Q3 due to the charges Q1 and Q2 (ii) Determine the direction of the force.
Answer: i) Fnet = 1129.51 N, ii) 64.62o
Continued...
b) Three +20 C charges are placed on a straight line, successive charges being 2 m apart as shown in Figure 2. Find
(i) the potential energy of the three charge system
(ii) the potential at point X
(iii) the work done to bring a -10 μC from infinity to point X . Answer: i) 4.5 J, ii) 4.2x105 V, iii) -4.2x10 J
Question 3 A
26 cm 36 cm B Q = -3.8 µC Figure 3
Point A is 26 cm north of a -3.8 µC point charge, and point B is 36 cm west of the charge as shown in Figure 3. Determine
(a) VB - VA
Answer: 3.7x104 V
Question 4
Two point charges of opposite sign and same magnitude 2.0 × 10-7 C are separated by a distance of 0.15 m. Find
(a) the total electric potential energy of these charges.
(b) the magnitude and direction of the electric field strength E at the mid-point between the charges.
(c) the magnitude and
Question 1
a) Two point of charges of opposite sign and same magnitude 3.5 μC are separated by a distance of 5 cm. Find (i) the magnitude and direction of the electric field strength, E at the midpoint between the charges. (ii) the magnitude and direction of the force F on an electron placed at the midpoint. Answer: i) E net = 1.008x108 N/C toward the –ve charge ii) F net = 1.6128x10-11 N toward +ve charge
Question 2
a) Based on Figure 1 above, the values for Q1, Q2 and Q3 are -86 μC, +50 μC and +65 μC respectively.
(i) Calculate the net electrostatic force on charge Q3 due to the charges Q1 and Q2 (ii) Determine the direction of the force.
Answer: i) Fnet = 1129.51 N, ii) 64.62o
Continued...
b) Three +20 C charges are placed on a straight line, successive charges being 2 m apart as shown in Figure 2. Find
(i) the potential energy of the three charge system
(ii) the potential at point X
(iii) the work done to bring a -10 μC from infinity to point X . Answer: i) 4.5 J, ii) 4.2x105 V, iii) -4.2x10 J
Question 3 A
26 cm 36 cm B Q = -3.8 µC Figure 3
Point A is 26 cm north of a -3.8 µC point charge, and point B is 36 cm west of the charge as shown in Figure 3. Determine
(a) VB - VA
Answer: 3.7x104 V
Question 4
Two point charges of opposite sign and same magnitude 2.0 × 10-7 C are separated by a distance of 0.15 m. Find
(a) the total electric potential energy of these charges.
(b) the magnitude and direction of the electric field strength E at the mid-point between the charges.
(c) the magnitude and