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Midterm10 solution

# Midterm10 solution - of the four corners of a square as...

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PHYSICS 142B – Virtual Midterm Exam Solutions 1. Two charged objects are 4.00 m apart. One object has a mass M 1 = 2.00 mg and charge Q 1 = 3.00 μC, while the other object has a mass of M 2 = 5.00 mg and a charge of Q 2 = 2.00 μC. Both particles are simultaneously released from rest. Calculate the speed of the object with mass 2.00 mg after a very long time. Use conservation of energy and momentum as there will be two unknowns 2. A conducting spherical shell with inner radius a and outer radius b has a positive point charge Q at its centre as shown in the diagram below. The total charge on the conducting shell is – 3Q. Derive expressions for the E-field in terms of the distance r from the centre for the regions: r < a, a < r < b and r > b. a b Q Conducting shell (-3Q)

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3. Three long parallel wires are perpendicular to the plane of the drawing and pass through three

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Unformatted text preview: of the four corners of a square, as shown in the diagram below. The side of the square is 2.010306 cm. The two wires through the opposite corners have identical currents, I 1 = I 2 = 6.00 A. (a) What should be the current in the third wire so that the B-field at the fourth (empty) corner is zero? (b) What is the direction of the magnetic force on the third wire? I 3 = ? I 1 (into page) I 2 (into page) 4. Consider the circuit shown. (a) The capacitor is fully charged. (i) Calculate the currents in all resistors. (ii) What is the charge on the capacitor? switch 50 μF 10 Ω 30 Ω 9 V 20 Ω 40 ω (b) After fully charging the capacitor, the switch S is now opened. After how long from the moment the switch is opened will the charge on the capacitor be equal to ¼ of its initial value?...
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Midterm10 solution - of the four corners of a square as...

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