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TUTORIAL 2 [UNIT 4 PHYSICS ON THE MOVE 4.2

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1. When two positive charges of magnitude Q1and Q2respectively are placed a distance rapart in a vacuum, theyexert a force on each other.

a. Write down the equation giving the magnitude Fof theforce the charges exert on each other. Identify any othersymbols used.

b. State whether this force is attractive or repulsive.Explain.

. !igure below shows point charges of magnitude +Q and+2Qrespectively.

. .+Q +2Q

a. S"etch the pattern of the electrical #eld around andbetween the charges.

b. !or this arrangement of charges, there is a point atwhich the electric #eld intensity is $ero. %n the #gureabove, mar" an Xon the approximate position of this

point.

&. !igure below shows a charged capacitor connected in a circuitwith a resistor and a switch.

a. What e'ect does the resistor have on the discharge ofthe capacitor(

b. Initially, before the switch is closed, the potentialdi'erence across the capacitor V0and the charge on theplates is Q0. )t time t*+, the switch is closed. %n the#gure below, s"etch a graph showing the variation ofthe charge Qwith time tfrom the moment the switch isclosed until the capacitor is e'ectively discharged. abelQ0on the curve.

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c. What is the name given to the shape of this graph(d. Explain what is meant by the tim !"#$t%#tof the

circuit.

e. -he capacitor in the circuit has a capacitance /p! andthe resistor has resistance 0. 2ow long after theswitch is closed will it ta"e for the potential di'erenceacross the capacitor to fall to 13 of its initial value(

. When a current is passed through a conductor, a magnetic#eld is created.

a. !igure below illustrates a long straight wire carrying acurrent normally out of the plane of the paper. S"etchthe pattern of the magnetic #eld associated with thiscurrent4carrying conductor.

b. -he same conductor 5in a.6 carries a current of 7.+ )and is placed perpendicular to a uniform #eld as shownbelow. In what direction is the force on the current4carrying conductor(

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TUTORIAL 2 [UNIT 4 PHYSICS ON THE MOVE 4.2

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c. -he length of the wire in the #eld is 1+cm and itexperiences a force of magnitude + m8. 9alculate themagnetic :ux density of the #eld.

1 a.

b.

a.

b.

&a

&b.

&cde.

abc

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