2019 - JAMB Physics Past Questions and Answers - page 3
When the downward current flows in a straight vertical conductor, the direction of its magnetic field at a point due north of the wire is
Upward
North
South
West
At the North point of the wire, the magnetic field is due east, at a point due South of the wire, the magnetic field is due west.
Aluminium is sometimes used as the leaf of an electroscope because it
is a light material
is a good conductor
is a good insulator
can be converted into thin sheets
because aluminium can be moulded into a thin sheet-like thin leaf material that can diverge easily.
The diagram represents the stress-strain graph of a loaded wire. Which of these statements is correct?
At J, the wire becomes plastic
J is the yield point
L is the elastic limit
At K, the wire breaks
A supply of 400V is connected across capacitors of 3μf and 6μf in series. Calculate the charge
8 x 10\(^{-4}\)C
4 x 10\(^{-2}\)C
8 x 10\(^{-3}\)C
4 x 10\(^{-8}\)C
| C\(_T\) = | C\(_1\) × C\(_2\)
C\(_1\) + C\(_2\) |
| = | 3 × 6
3 + 6 |
= \(\frac{18}{9}\) = 2μf
Q = CV
⇒ 2 × 10\(^{-6}\) × 400
⇒ 800 × 10\(^{-6}\)C = 8 × 10\(^{-4}\)C
A vibrator causes water ripples to travel across the surface of a tank. The wave travels 50cm in 20s and the distance between successive crests is 5cm. Calculate the frequency of the vibrator
5Hz
6Hz
5.2Hz
25Hz
| V = | distance
time |
= | 50 cm
25 |
= | 25 cm/s |
V = fλ
hence,
| f | = | V.λ |
| = | 25
5 |
= | 5Hz |
f = 5Hz
A thermocouple thermometer is connected to a millivoltmeter which can read up to 10mV. When one junction is in ice at 0°C and the other is steam at 100°C, the millivoltmeter reads 4mV. What is the maximum temperature which this arrangement can measure
100\(^o\)C
248\(^o\)C
250\(^o\)C
350\(^o\)C
t\(_\theta\) - t\(_o\) = 10,
t\(_{100}\) - t\(_o\) = 4
| θ = | t\(_\theta\) - t\(_o\)
t\(_{100}\) - t\(_o\) |
× | 100 |
| 10
4 |
× | 100 | = | 250°C |
θ = 250°C
An alternating current can induce voltage because it has
ripple value
varying magnetic field
weaker magnetic field than direct current
high peak value
The induced voltage produced by the varying magnetic field is proportional to the rate of change of magnetic flux linking the coil.
The limiting frictional force between two surfaces depends on
I. the normal reaction between the surfaces
II. the area of surface in contact
III. the relative velocity between the surfaces
IV. the nature of the surfaces
I only
II only
III only
I & IV only
friction depends on the normal reaction between the surfaces and the nature of the surfaces
During the transformation of matter from the solid to the liquid state, the heat supplied does not produce a temperature increase because
the heat energy is quickly conducted away
the heat capacity has become very large as the substance melts
the heat gained is equal to the heat lost by the substance
all the heat is used to break the bonds holding the molecules of the solid together
The process in which a solid changes to a liquid is called melting. The melting point is the temperature at which a solid changes to a liquid. For a given type of matter, the melting point is the same as the freezing point. During melting, the heat supplied does not produce a temperature increase because the heat is used to break the bonds holding the molecules of the solid together
The statement 'Heat lost by the hot body equals that gained by the cold one' is assumed when determining specific that heat capacity by the method of mixtures. Which of the following validates the assumption?
I. Lagging the Calorimeter
II. Ensuring that only S.I units are used
III. Weighing the calorimeter, the lid and the stirrer.
I only
I & II only
I & III only
II & III only
I. Lagging the Calorimeter and III. Weighing the calorimeter, the lid and the stirrer since their units are independent of the energy equation.