# 2004 JAMB Physics Past Questions & Answers - page 1

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1
If 16mA of current flows through a conductor in one second, the number of electron transported per seconds is

[1 electronic charge = 1.6 x 10

[1 electronic charge = 1.6 x 10

^{-19}C]
A 1.00 x 10

^{20}
B 2.56 x 10

^{-18}
C 2.56 x

^{-17}
D 1.00 x 10

^{17}**Correct Option:** D

**Solution**

^{q}/

_{t}→ q = i x t

= 16 x 10

^{-3}x 1

= 1.6 x 10

^{-2}C

But 1.6 x 10

^{-19}C = I electronic charge

1 coulomb = 1 / (1.6x10

^{-19})

∴ 1.6 x 10

^{-2}coulombs = 1 / (1.6x10

^{-19}) x 1.6x10

^{-2}/ 1

= 1.0 x 10

^{-2}x 10

^{19}

= 1.0 x 10

^{17}

2
Electrical appliances at home are normally earthed so that

A the appliances are maintained at a lower p.d than the earth

B both the a.c and d.c sources can be used

C a person touching the appliances is safe from electric shock

D the appliances are maintained at a higher p.d than the earth

**Correct Option:** C

3
Given three capacitors 0.3μF, 0.5μF and 0.2μF, the joint capacitance when arranged to give minimum capacitance is

A 0.1μF

B 0.3μF

C 1.0μF

D 0.5μF

**Correct Option:** A

**Solution**

^{1}/

_{C}=

^{1}/

_{0.3}+

^{1}/

_{0.5}+

^{1}/

_{0.2}= 10.3333

=> C = 1 / 10.3333 = 0.09677

≅ 0.1μF

∴ C = 0.1μF

4
The difference between X-rays and gamma rays is that

A x-rays are more penetrating than gamma rays

B x-rays are electromagnetic radiations while gamma rays are negatively charged radiation

C x-rays have higher frequencies than gamma rays

D x-rays arise from energy changes in the electronic structure of atoms while gamma rays come from the nucleus

**Correct Option:** D

5
To protect a material from the influnce of an external magnetic field, the materials should be kept

A square steel ring

B triangular zinc ring

C soft iron ring

D loop of copper wire

**Correct Option:** C

**Solution**

6
In the diagram above, the ratio of he electric power dissipated in the 6Ω and the 3Ω resistor respectively is

A 2:1

B 2:2

C 1:3

D 1:2

**Correct Option:** D

**Solution**

^{2}R;

and I =

^{E}/

_{R}

But effective Parallel resistance: is given by:

^{1}/

_{R}=

^{1}/

_{6}+

^{1}/

_{3}=

^{1+2}/

_{6}=

^{3}/

_{6}=> R =

^{6}/

_{3}= 2Ω

Current I =

^{E}/

_{R}=

^{12}/

_{2}= 6A

But I

_{1}= (

^{R1}/

_{R1+R2}) x 1 =

^{3}/

_{9}x 6 = 2A

again I

_{1}= (

^{R1}/

_{R1+R2}) x 1 =

^{6}/

_{9}x 6 = 4A

∴P

_{1}= I

_{1}

^{2}R

_{1}= 2 x 2 x 6 = 24W

P

_{2}= I

_{2}

^{2}R

_{2}= 4 x 4 x 3 = 48W

thus

^{P1}/

_{P2}=

^{24}/

_{48}=

^{1}/

_{2}; OR P

_{1}: P

_{2}= 1:2

7
If the angle between two vector P and Q is O

^{o}, the vectors are said to
A intersect at the angle 45

^{o}
B intersect at the angle 60

^{o}
C be parallel

D be perpendicular

**Correct Option:** C

8
A body of mass 4kg is acted on by a constant force of 12N for 3 seconds. The kinetic energy gained by the body at the end of the time is

A 144J

B 162J

C 81J

D 72J

**Correct Option:** B

**Solution**

^{1}/

_{2}MV

^{2}

Force, F = ma => a =

^{F}/

_{m}=

^{12}/

_{4}= 3ms

^{-2}

But a = (V-U) / t => V = u + at

If the initial velocity U = 0, then V = at = 3 x 3 = 9ms

^{-2}

∴ K.E, =

^{1}/

_{2}ms

^{-2}

^{1}/

_{2}4 x 9 x 9 = 162J

9
A machine whose efficiency is 60% has a velocity ratio of 5. If a force of 500N is applied to lift a load P, what is the magnitude of P?

A 1500N

B 500N

C 4166N

D 750N

**Correct Option:** A

**Solution**

^{60}/

_{100}=

^{M.A}/

_{5}

∴M.A = (60 X 5) / 100 = 3

But M.A = Load/Effort; => 3 = Load/500

∴Load = 500 x 3

= 1500N

10

Which of the above is based on Newton's third law of motion

**I. Jet propelled aircraft**

II. Rocket propulsion

III. The recoil of a gun

IV. A person walkingII. Rocket propulsion

III. The recoil of a gun

IV. A person walking

Which of the above is based on Newton's third law of motion

A I and II only

B I, II, III, and IV only

C I and III only

D I, II and III only

**Correct Option:** D

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