7. An airplane is flying through a thundercloud at a height of 2000 m. If there is charge concentrations of 40 C at a height of 3000 m and -40 C at a height of 2000 m, what is the electric field experienced by the airplane? [7.19 x 105 N/C]

8. Three charges of Q1=3 nC, Q2=8 nC and Q3=-5 nC are distributed on an equilateral triangle as seen in the figure below with equal distance of r=500 mm and θ=60°. Calculate the midway electric field between charges Q2 and Q3. [1.875 x 103 N/C, 4.4° below +x axis]

9. A plastic ball of mass 2 g is suspended by a string on length 20 cm in a horizontal electric field with strength of 1 x 103 N/C, as shown in the figure below. If the ball is in equilibrium when the string makes a 15° angle, what is the net charge distributed on the ball? [5.25 μC]

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10. Charges Q1=6 nC and Q2=3- nC are separated at a distance of 60 cm. The third charge, Q3=12 nC is to be placed at an appropriate distance so that the net electrostatic force among all the three charges will be zero. Find the position of Q3 to be placed. [1.45 m after Q2]

11.An electron is accelerated by a constant electric field of magnitude 300 N/C.

a) Find the acceleration of the electron [5.27 x 1013 m/s2]

b) With the answer from a), find the electron’s speed assuming it starts from

rest with t=1 x 10-8 s [5.27 x 105 m/s]

12.In a particle beam, a proton has a kinetic energy of 3.25 x 10-15 J. What is the

magnitude of the electric field that will stop the proton in 125 cm? [1.63 x 104

N/C]

13.A proton accelerates from rest in a uniform electric field of 640 N/C. At a finite amount of time, its speed is 1.2 x 106 m/s.

a) Find the magnitude of the acceleration of the proton [6.12 x 1010 m/s2]

b) How long does it take for the proton to reach 1.2 x 106 m/s? [19.6 μs]

c) How far the proton would have moved in that interval? [11.8 m]

d) What is its final kinetic energy? [1.2 x 10-15 J]

14. Figure below shows an electrostatic deflection system consisting of two parallel

plates, each of 2.5 cm in length with a separation distance of 0.40 cm. The centre of the plates is situated 20 cm from a screen. A potential difference of 60 V is applied between the plates which creates an electric field in between the plates. An electron of speed 3.1 x 107 m/s enters the region at right angle to the field. With this information given, calculate

a) Time taken for the electron to pass through the plates [8.06 x 10-10 s]

b) Electric field strength between the plates [1.5 x 104 N/C downwards]

c) Force on the electron due to the electric field [2.4 x 10-15 N upwards]

d) Acceleration of the electron along the direction of the electric field [2.64 x

1015 m/s upwards]

e) Verticalcomponentofvelocityofelectronwhenitleavestheregionbetween the plates [2.13 x 106 m/s]

15.Two parallel plates are illustrated below that have a uniform electric field of 6100 N/C and directed to the right. A charge of +1e with mass of 1.67 x 10-27 kg is inserted between the two plates.

a) Find the electric force exerted on the charge [9.76 x 10-16 N towards the

right]

b) Find the acceleration of the charge [5.84 x 1011 m/s2]

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c) Are the direction of the electric force and charge the same? Justify your answer.

d) Calculate the potential differences between the two parallel plates [305 V]

e) Calculatetheworkdonebytheelectricforcetomovethechargefrompoint

A to point B with the distance ‘d’ [4.88 x 10-17 J]

16.A positive charge of +9 x 10-9 C is located at the origin. How much of work is required to bring a positive charge of +3 x 10-9 C from infinity to the location x = 30 cm? [8.09 x 10-7 J]

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