Physics Paper 3 WASSCE (SC), 2016

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)