An Empire starship fires at Skywalker’s ship


An Empire starship fires a beam of electrons at Skywalker’s ship. Each electron has an initial kinetic energy of 1.6×10−17 J. The Skywalker’s ship has been fitted out with the electrostatic shield technology for defense against electron beam weapons. The electric field of the shield points directly inward. If the electrons stop after travelling 83 m, what is the size of the electric field generated by the ship’s shield? Please ignore relativistic effects.

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The resistance of each resistor

The total resistance of the circuit is 10 Ω. If the resistors R1 and R3 are swapped then the total resistance of the circuit will increase 100 times. If the resistors R2 and R3 are swapped then the total resistance of the circuit will increase by 0.2%.


Find the resistance of each resistor.

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The Ring


A homogeneous wire is used to make a ring with a jumper on the diameter AB. What is the percentage change in the resistance between points A and B, if the jumper is cut?
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Which of the bulbs will fuse?

DC1Two electric bulbs marked 25W – 220V and 100W – 220V are connected in series to a 440V supply. Which of the bulbs will fuse?

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The path of an electron in a bubble chamber

70l9eThe diagram shows the path of an electron in a bubble chamber.

Which of the following can you deduce from the diagram?


(A) The electron is moving anti-clockwise.
(B) The electron is moving clockwise.
(C) The magnetic field is acting out of the page.
(D) The speed of the electron is increasing.

Source: The Student Room

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Radius of the circular path described by a proton

ProtonInMagnetFieldProtons having a kinetic energy of 20 keV are moving in a plane perpendicular to a magnetic field B = 0.05 T directed out of the plane.
Find the radius of the circular path.

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How will the spheres be charged, if at all?

Rod2Spheresv3Two uncharged conducting spheres, A and B, are suspended from insulating threads so that they touch each other. While a positively charged rod is near A (not touching sphere A), the spheres are moved apart. How will the spheres be charged, if at all?

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