3 Two point charges A and B each have a charge of +6.4 x 10-19 C....

 

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3 Two point charges A and B each have a charge of +6.4 x 10-19 C. They are separated in a vacuum by a distance of 12.0m, as shown in Fig. 17.5. +6.4 x 10-19 CA P Fig. 17.5 3.0 m 12.0 B +6.4 x 10-19 C 3.0 m ! Points P and Q are situated on the line AB. Point P is 3.0m from charge A and point sphere A Qis 3.0m from charge B. a Calculate the force of repulsion between the charges A and B. b Explain why, without any calculation, when a small test charge is moved [3] from point P to point Q, the net work done is zero. [2] c Calculate the work done by an electron in moving from the midpoint of line AB to point P. [4] Cambridge International AS and A Level Physics, 9702/42 May/June 2010 Q4 3 Two point charges A and B each have a charge of +6.4 x 10-19 C. They are separated in a vacuum by a distance of 12.0m, as shown in Fig. 17.5. +6.4 x 10-19 CA P Fig. 17.5 3.0 m 12.0 B +6.4 x 10-19 C 3.0 m ! Points P and Q are situated on the line AB. Point P is 3.0m from charge A and point sphere A Qis 3.0m from charge B. a Calculate the force of repulsion between the charges A and B. b Explain why, without any calculation, when a small test charge is moved [3] from point P to point Q, the net work done is zero. [2] c Calculate the work done by an electron in moving from the midpoint of line AB to point P. [4] Cambridge International AS and A Level Physics, 9702/42 May/June 2010 Q4