2008 - JAMB Physics Past Questions and Answers - page 4

To correct and A.C generator with a D.C generator the slip ring is replaced with split-ring communicator

Efficiency = (power output)/power input x 100%
= 1_s V_S x 100% 1_p
V_p
∴ (80)/100 = (50)/I_P x 200
I P = (50 x 100)/80 x 200 = 3.125 A

Max kinetic energy = Energy of incident electron - work function. EK = hf - w
= 6.6 x 10^-34 x 6.7 x 10¹⁴ - 3 x 10^-19
= 4.422 x 10^-19 - 3 x 10^-19
= 1.422 x 10^-19J

Zener diode is useful in stabilized power supply i.e to keep steady the voltage of a power supply.

Heating a pure semiconductor increases the mobility of electrons and holes and hence the conductivity. thus, the resistance decreases on heating

Transistor is used for amplification of current, power and as a switch in logic gates.

Electrical work W = QE,
Where Q is the quantity of change and E is the electromotive force.
∴ E = W = FxDQ_It
Where D is the displacement,I = current and t = time
But dimension of force,
= unit of mass x unit of Acceleration
= unit of mass xunit of velocityunit of time
= unit of mass x unit of displacement__unit of time x unit of time
ML/T² = MLT^-2
∴ Dimension of emf E
= MLT^-2L = ML²T^-3I^-1__IT

R² - P² + Q² = 12² + 5²
= 144 + 25 = 169
∴R = √169 = 13N
∴ angle between the forces is 90^o

The force which is centripetal
F = MV²_R
=5 x 7²3.5
= 70
V = √(Fr) and if F is tripped, then
V = √(3Fr)/m
= √(3x70x3.5)/5
= 12.1ms^-1

Smooth plane has negligible friction
∴ only the resultant of the perpendicular forces is acting on the body, which is given as
F =
√ 8² + 6² 

=
√ 64 + 36 

=
√ 100 

= 10N
But F = Ma
∴ a = ^F/_M = ¹⁰/₄ = 2.5 ms^-1