Transcript Slide 1
Which is the correct expression for work done in moving a particle of charge q from a to b against an electric field E , when the particle is not accelerated? b (a) W qE dx a b (b) W qE dx a a b (c) W E dx a b (d) W E dx a (e) none of the above q b E Which of the equations given below are correct? 1. Electrical potential = potential energy of a charge q potential energy of a charge q 2. Electrical potential = q work done to move a charge q 3. Change in electrical potential = q 4. Change in electrical potential = - E ds (a) All of them (b) 2, 3 & 4 (c) 1, 2 & 4 (d) 1, 3 & 4 (e) 2 & 4 A negative charge -Q is placed on a conducting sphere. -Q b a c 1. At which of the points a, b, or c is the electrical potential the lowest? (a) a (b) b (c) c 2. At which of the points a, b, or c is the electrical potential the highest? (a) a (b) b (c) c A positive charge +Q and a negative charge –q are separated by a distance d, and the potential VP = 0 at point P. This means that: +Q P -q d a) No force is acting on a test charge placed at point P. b) The electric field must be zero at point P. c) The net work in bringing Q to a distance d from q is zero. d) The net work needed to bring a charge from infinity to point P is zero. E 4 1 2 3 Which two points shown in the diagram are at the same potential? a) 1 and 3 b) 2 and 3 c) 1 and 4 d) 2 and 4 Which of the points shown in the diagram is at the highest potential? a) 1 b) 2 c) 3 d) 4 The electric potential at a distance r from the center of a spherical charge of radius R and charge Q is given by the equation on the right. 1. The zero potential is taken at (a) the center of the sphere (b) the surface of the sphere (c) infinite distance from the sphere +Q ke Q V (r ) r r 2. A charge q is brought towards a spherical charge Q, as shown below. The direction of the potential energy of charge q is: (a) to the right b) to the left (c) neither: energy is a scalar Q q A positive q is moved to within a distance r1 from charge Q1 and r2 from charge Q2 Q1 r1 Q2 r2 The potential energy of q (relative to zero at infinity) is: a) b) c) d) ke Q1 ke Q2 r1 r2 ke Q1q ke Q2 q r1 r2 ke Q1q kQq cos1 e 2 cos2 r1 r2 none of the above q 2 1 The potential difference between the cathode and the screen of a traditional TV is 12 kV. What is the speed of an electron just before it hits the screen? a) 8.8 107 m/s b) 6.5107 m/s c) 4.2107 m/s d) 7.710 m/s 7 e) 5.3107 m/s F1 Three positive charges q1, q2, q3 are arranged as shown on the right, where Fi is the force on charge qi, and rij is the distance between charges i and j. q2 r12 q1 r23 r13 The total potential energy of the system is (a) ( F1 F2 F3 ) (r12 r13 r23 ) q1q2 q1q3 q2 q3 (b) ke 2 ke 2 ke 2 r12 r13 r23 q1q2 q1q3 q2 q3 (c) ke ke ke r12 r13 r23 (d) Can't tell without knowing the angles. q3 F3 F2