2017 - JAMB Physics Past Questions and Answers - page 2

Efficiency = \(\frac{ma}{V.R}\) x \(\frac{100}{1}\)

V.R = number of pulleys = 6

ma = \(\frac{\text{Load}}{\text{Effort}}\) = \(\frac{200}{50}\) = 4

Effiecieny = \(\frac{4}{6}\) × 100 = 66.67%

Resistor connected in a parallel have an equivalence given by
\(\frac{1}{\text{Reff}}\) = \(\frac{1}{3}\) + \(\frac{1}{3}\) + \(\frac{1}{3}\)

= \(\frac{1 + 1 + 1}{3}\) = \(\frac{3}{3}\) = 1

Reff = 1ω

Compressor is an instrument to supply air or other gas at increased pressure
Refrigerator is an appliance to keep things cold
Air blower is used to release air
Air conditioner is used to remove heat and maintain a stable temperature in an occupied space

Isotopy is due to difference in mass number, what causes the difference is the difference in the number of neutrons present

Thermal expansion of a solid is majorly advantageous in the use of bimetallic strip in the balance of a watch so as not to lose time

Moment of a force is the product of a force and the perpendicular distance from the line of action of the force
Moment = force × distance
= N × m
= Nm

Magnification = \(\frac{\text{Length of camera}}{\text{distance of object from pin hole}}\)

m = \(\frac{12}{60}\)

= 0.2

Also magnification m = \(\frac{\text{Height of image}}{\text{Height of object}}\)

∴ Height of image = m × height of object

= 0.2 × 70

= 14cm

H = mcθ

H_P = H_Q, θ_P = 2θ,

m_P = \(\frac{1}{2}\)m_Q

∴ H_P = m_QC_Pθ_P, also HQ = m_QC_Qθ_Q

Since H_P = H_Q

∴ m_Pc_Pθ_P = m_Qc_Pθ_q

Putting in the conditions

\(\frac{1}{2}\)m_Q × c_P × 2θ_Q = m_Q × θ_Q × c_Q

∴ c_P = c_Q

\(\frac{C_p}{C_Q}\)= \(\frac{1}{1}\)

= 1:1

The relationship between the peak value and r.m.s value of electricity supply is given as

V\(_{r.m.s}\) = \(\frac{V_o}{\sqrt{2}}\)

where V_o = peak voltage

∴ V_o = V\(_{r.m.s}\) × √2

= 240 × √2

= 339.5v

= 340v