Question 3B
(i) State two methods by which an electric current can be produced.
(ii)
Calculate the value of R in the circuit diagram shown above, given that the effective resistance of the circuit is 4.0 Ω and the internal resistance of the cell is negligible.
Observation
Part (b) Candidates responded satisfactorily in this part.
The expected answers are:
- Measure and record five values of E to at least 1 d.p in volts
- Read and record five values of V to at least 1 d.p in volts and in trend
- Read and record five values of to at least 1 d.p in ampere and in trend
- Evaluate five values of to at least 3.d.p
- Evaluate five values of to at least 3 d.p
- Show composite table containing at least E, V, I,and
- Plot a graph using reasonable scale
- Draw line of best fit
- Determine the slope of the graph and intercept
- State any two of the following precautions
e.g
- Ensured clean terminals/tight connections
- Key removed after taking each reading/key removed when reading was not being taken
- Avoided parallax error on Voltmeter/Ammeter
- Noted/corrected zero error on voltmeter/ammeter
- Repeated readings (shown on the table)
b(i) Production of electric current
e.g use of
cells (accumulators/simple cells)/fuel cells
generators/dynamos/electromagnetic induction
solar cells/photocells
windmills
tidal waves
geothermal/thermal
gas turbines
hydro power
nuclear power
thermocouple/thermopile/thermionic
piezo electric generators
electrostatic generator (e.g Van de graff generator)