Exam q: (static) electricity

Question 1

A student did an experiment with two strips of polythene. She held the strips together at one end. She rubbed down one strip with a dry cloth. Then she rubbed down the other strip with the dry cloth. Still holding the ends together, she held up the strips
What movement would you expect to see?

Answer 1

The strips moving away from each other.

Question 2

A student did an experiment with two strips of polythene. She held the strips together at one end. She rubbed down one strip with a dry cloth. Then she rubbed down the other strip with the dry cloth. Still holding the ends together, she held up the strips. The strips moved away from each other. Why?

Answer 2

The strips are charged similarly (have the same charge) so repel

Question 3

Complete the sentences: Each strip has a negative charge. The cloth is left with a ___ charge. This is because particles called _____ have been transferred from the ___ to the ___

Answer 3

positive, electrons, cloth, strip

Question 4

Complete the sentence: Materials, such as aluminium, which electricity will pass through easily, are called ___

Answer 4

conductors

Question 5

Complete the sentence: Materials, such as polythene which electricity will not pass through easily, are called ____

Answer 5

insulators

Question 6

A simple series circuit contains two resistors of 9 ohms and 6 ohms. Calculate the total resistance of the two resistors in the circuit.

Answer 6

9 + 6 = 15Ω
15Ω

Question 7

If I = 0.3 A and R = 15Ω, what is V?

Answer 7

V = IR
V = ? I = 0.3 A R = 15Ω
0.3 x 15 = 4.5
V = 4.5 V

Question 8

Complete the sentence: Replacing a resistor with a resistor of higher value will ____ the reading on the ammeter

Answer 8

decrease

Question 9

8 identical filament lamps were connected together to a 12 V power supply
Calculate the potential difference across each lamp

Answer 9

12 / 8 = 1.5
1.5 V

Question 10

A filament lamp has a potential difference across it of 1.5 V, and a power output of 0.75 W.
Calculate the resistance.

Answer 10

P = V^2 / R
1.5 x 1.5 = 2.25 V
R = 2.23 / 0.75 = 3Ω

Question 11

Explain the method a student could use to investigate how the resistance of a single lamp changes with the potential difference across the lamp.

Answer 11

-Firstly, the student would connect the circuit using the components: cells, variable resistor, ammeter, voltmeter, filament lamp
- Then the student would use the variable resistor to change the potential difference in parallel across the lamp to 0.5 V
- The student would record the current reading on the ammeter in series through the lamp and the potential difference on the voltmeter across it
- Using R = V/I, the student could calculate resistance
- The student should repeat this process with a number of voltages and then should switch the direction of current and repeat the process
- A variable power supply could be used instead of a variable resistor to vary voltage.