WAEC PHYSICS PRACTICAL ALT CONFIRMED ANSWERS 2020
Here on this page is the physics answers for practical alternative for 2020 waec examination. Like i always advice, make sure each question corresponds with the answer before you write it, you can make yours a bit unique. good luck and stay tuned. this page will be updated regularly.
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Observation W = ????
I°,d(cm),L(cm),e/°,Φ/°,Φ = I + e/° any one asked ??️?️?
Scale eg. Let 2cm represent 0.1unit on cos Φ axis
Let 4cm represent 0.1unit on sin I axis
Depending on what you are ask to place on the graph ??
**Intercept on the vertical/horizontal axis if asked.?
I. I ensured neat traces by using sharp pencil.
II. I ensure that the pins are vertically erect.
III. I ensure that the pins are well spaced which is 4cm apart.
IV. I avoided parallax errors when reading protractor.
V. I avoided error due to parallax when reading the metre rule.
*Choose any asked*
A. State the conditions necessary for total internal reflection of light to occur.
B. The Critical angle for a transparent substance is 39°. Calculate the refractive index of the substance.
C. State snell’s law
D. Calculator the critical angle for a water – air interface [ refractive index of water = 4/3 ]
A. I. Light must be traveling from a denser medium to a less dense medium.
II. The angle of incidence in the dense medium must be greater than the critical angle.
B. Refractive index (n) = 1/sinC = 1/Sin39° = 1/0.6293 Therefore, n = 1.59
C. Snell’s law state that the ratio of the angle of refraction is a constant for a given pair of media.
D. 1/SinC = a ^N w Therefore, SinC = 3/4 = 0.75 Hence C = Sin inverse 0.75 = 48.6
I. I ensured Tight connections.
II. I noted the zero error on the ammeter and voltmeter.
III. I avoided error due to parallax when reading the ammeter and voltmeter.
IV. I ensured that I remove the key when readings are not been taken to prevent the cells from running down.
*Study this incase if asked* ??
A. Two method by which electric current can be produced
B. Explain why E. M. F. of a cell is greater than the PD. across the cell when it is supplying current though an external resistance
C. Define potential difference between two points in an electric circuit.
A. Electric current can be provided using:
I. Chemical Cells
III. Solar Cells
IV. Gas Turbines
V. Hydro Power
VI. Wind Mills
Viii. Nuclear Power
B. E. M. F. (E) is the Work done across external resistance (R) and internal resistance of the cell (r) While (PD) [v] is the work done across external resistance (R) only, hence, emf of a cell is greater than the PD across the cell.
Therefore, E = V + Ir
C. The potential difference between two points in an electric circuit is the Work done in Joules (J) in moving a charge of one Coulomb (c) from one point to the other..