The West African Examinations Council WAEC Physics Questions Answers 2021 Objective and Theory Update.
Workdone = 1/2Fe
= 1/2 × 40 × 1/100
= 1/5 = 0.2J
(i)Navigation satellites e.g global position system – GPS
(ii) Communication satellites eg ANIK
V = 2πR/T
For every second,
Speed, V = 2πR
V = 2 × 22/7 × 6300
V = 39,600km/s
The scientific principle underlying the operation of a fibre optics is the principle of total internal reflection by which light signals can be transmitted from one place to another with a negligible loss of energy.
Core: The core is the light transmission area of the fibre, either glass or plastic cladding. The function of the cladding is to provide a lower refractive index at the core interface in order to cause reflection within the core so as to enable light waves transmitted through the fibre.
Cladding: It functions as a gadget that provides a clear refractive index at the core interface in order to cause reflection within the core so that light waves are transmitted through the fibre.
Hooke’s law states that the extension e produced by an elastic material is directly proportional to the applied force provided the elastic unit is not exceeded.
(i) Given extension, e = I2 – I1 = 0.75 – 0.20 = 0.55m
Force applied, Fe = (1.95 – 0.30) × 10
= 1.65 × 10 = 16.5N
Force constant , K = F/R = 16.5/0.55 = 30N/m
(ii) Using F = K (I1 – Io)
m1g = K ( I1 – Io)
= 0.30 × 10 = 30(0.20 – Io)
= 0.10 = 0.20 – Io
Io = 0.20 – 0.10
Io = 0.10m
Length of spring when it was unloaded = 0.10m
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.
(ii) Size of particles
Rate of diffusion is inversely proportional to the square root of density under given conditions of temperature and pressure. ie R ∝ 1/√d
T = circumference of the orbit/orbit velocity
T = 2πR/v
But V = √GM/R
T = 2π√R³/GM
Root measurement value of an alternating current is the value of A.C current that has the same heating affect as a D.C current
Impedance is the affective resistance of an electric circuit arising from the combined affects of ohmic resistance and reactance. (i.e resistors, indicators and capacitors)
Current in circuit , I = 60/120 = 0.5A
Voltage across device , Vr = 120V
Voltage across capacitor , Vc = √V² – Vr
Vc = √240² – 120²
Vc = 207.846V
Ic = I = 0.5
Xc = Vc/Ic = 207.846/0.5 = 415.7Ω
Capacitance, C = Xc/2πf = 415.7/23.14250 = 1.323F
The capacitance of a capacitor is the ratio of the amount of charge on its plates to the potential difference between them. ie C = ∑/V
(i) Charge in both capacitors are the same
∑1 = Q2
ie C1V1 = C2V2 ………(1)
Total capacitance ,C = C1C2/C1+C2
C = C2/1+C2/C1 = C2/1+V/V2
C = C2V2/V1+V2 = C2V2/2
(ii)Voltage across, V1 = (C2/C1+C2) × V
V1 = (C1/C1+C2) × V
But C1/C2 = d2/d1 = 5/2
V1 = (1/(5/2+1)) × 2 = 2/7 ×2 = 4/7Volts.