JAMB Physics Past Questions & Answers - Page 158

786.

The r.m.s value of a supply voltage is quoted at 200v. What is the approximate peak value of the voltage?

A.

200volts

B.

300volts

C.

283volts

D.

250volts

Correct answer is C

Vr.m.s = V0 ÷ V2, where Vr.m.s rep. to as voltage root –square mean, v = peak voltage

Vr.m.s = 200volt, v = ?

200 = V0 ÷ V2

V0 = 200v2

= 200 × 1.414

= 282.8 volts V0 = b &approx.; 283 volts

787.

A good electric cell should have the following except

A.

A minimum of polarization effect

B.

A long life

C.

A cheap and safe electrolytes

D.

Cost and dangerous of the cell

Correct answer is D

A good electric cell should proses the following

1. A long life of an electric cell,

2. A minimum of polarization effect

3. A cheap and safe electrolytes

Except D cost and dangerous of the electric cell

788.

The dimension of universal gravitational constant is……….?

A.

\( M­^{–1}L^3 T^{–2} \)

B.

ML3T2

C.

ML3

D.

MLT-2

Correct answer is A

f α (MM ÷g2)

F(GMM ÷ r2) [G – gravitational constant]

GMM = Fr2

G = F02 ÷ MM = m × aπr2 ÷ MM (f = ma)

= (m × m5-2 × r2) ÷ MM

= (Kg.m52 × m2) ÷ Kg.Kg

=1 ÷ kg.m3.52

The dimension mathematically representation have a quantities of M, L AND T

M (Mass) = kg, L (Length) = M, T (Time) second

G = kg-1 m2.52(Using dimension rule)

M-1.L3.T-2

∴ The universal gravitational constant (G) =\( M­^{–1}L^3 T^{–2} \)

789.

For a best result using temperature to achieve an accurate measurement, it is best to use

A.

Mercury thermometer

B.

gas thermometer

C.

clinical thermometer

D.

alcohol thermometer

Correct answer is B

Gas thermometers are considered best for use to achieve an accurate temperature than others, such as liquid in glass thermometers such as mercury, clinical and alcohol thermometer

790.

What is the S.I unit of relative density?

A.

kg m-2

B.

kg m2

C.

kg cm3

D.

has no S.I unit

Correct answer is D

Note: relative density has no S.I unit

∴ Relative density = weight of substance ÷ weight of equal volume of water

RD = w1 ÷ (w1 – w2) (no S. I unit)