P2 Revision Booklet

Static Electricity

Harder (Grade B-A*)

Q1.          (a)    The diagram shows a student touching the metal dome of a Van de Graaff generator.
When the generator is switched on, the metal dome becomes negatively charged.

Explain why the student’s hair stands on end when the generator is switched on.
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(2)

(b)     When the potential difference between the student and a nearby earthed metal dome reached 15 kV, a spark jumped between the student and the earthed dome. The spark transformed 30 mJ of energy into heat, light and sound. (1 mJ = 0.001 J)
Use the equation in the box to calculate the charge carried by the spark.
 
energy transformed   =   potential difference   ×   charge	

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           Charge transferred =.................................................. coulombs
(2)

(c)     What name is given to the rate of flow of charge?
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(1)
(Total 5 marks)
 Q2.          The drawing shows an experiment using a low voltage supply, a joulemeter, a small immersion heater and a container filled with water.

          The voltage was set at 6 V d.c. The reading on the joulemeter at the start of the experiment was 78 882 and 5 minutes later it was 80 142.
(i)      Use the equation:
voltage = 
          to work out the total charge which flowed through the immersion heater in five minutes. Clearly show how you get to your answer and give the unit.
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Charge = ............................................
(3)

(ii)      Calculate the current through the immersion heater during the 5 minutes. Write the equation you are going to use, show clearly how you get to your answer and give the unit.
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Current = .........................................
(3)
(Total 6 marks)
 
Q3.          The diagram shows apparatus used to demonstrate the electric motor effect. When he switch is closed the wire moves.

(i)      Draw an arrow on the diagram to show the direction the wire moves.
(1)

(ii)      Explain why the wire moves.
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(2)
(Total 3 marks)
 Static electricity-Mark scheme

M1.          (a)     each hair gains the same (type of) chargeor(each) hair is negatively charged
do not accept hair becomes positively charged
or(each) hair gains electrons
1

similar charges repel
accept positive charges repel
providing first marking point is in terms of positive charge
ornegative charges repelorelectrons repel
1

(b)     0.000002
accept correct substitution and transformation for 1 mark
or 2 × 10-6
ie 30 / 15 or .03 / 15000 or 30 / 15000 or .03 / 15
or 2 μ C
answers 2 and 0.002 gain 1 mark
2
(c)     current
do not accept amp / amperes
1
[5]
 M2.          (i)      either
210 C
3
          or
1260 (joules of energy transferred)
unit not required
1
          210
1
          coulomb(s) C
allow J/V
1

(ii)      either
0.7 A
3
          or
charge = current × time
or 210* = current × 300
1
          or Q = It
or* same as candidate’s answer to
part (a)(I) provided correct unit given in part (a)(i)
or* as follows from above
1
          current = 0.7*
amp(s) or A
1
[6]
 M3.          (i)      away from magnet
arrow should be perpendicular to field lines and current as judged by eye
1

(ii)      current in wire creates magnetic field around wire
1
          two fields interact or combine giving a resultant force (on the wire)
1
[3