Physics 2017 Jamb Examination

To find the cost, we first calculate the total energy consumed in kilowatt-hours (kWh).
1. Calculate total power in Watts:\[ P = (7 \times 40\text{W}) + (5 \times 80\text{W}) = 280\text{W} + 400\text{W} = 680\text{W} \]2. Convert power to kilowatts:\[ 680\text{W} / 1000 = 0.68\text{kW} \]3. Calculate energy (kWh) for 12 hours:\[ E = P \times t = 0.68\text{kW} \times 12\text{h} = 8.16\text{kWh} \]4. Calculate cost:\[ \text{Cost} = 8.16\text{kWh} \times \text{N}7.00 = \text{N}57.12 \]

Total Current Calculation for Parallel Circuit\[\text{Using Ohm's Law: } I = \frac{V}{R}\]\[\text{Branch 1: } I_1 = \frac{12\text{V}}{6\Omega} = 2\text{A}\]\[\text{Branch 2: } I_2 = \frac{12\text{V}}{12\Omega} = 1\text{A}\]\[\text{Branch 3: } I_3 = \frac{12\text{V}}{18\Omega} = 0.67\text{A}\]\[\text{Total Current (KCL):}\]\[I_T = I_1 + I_2 + I_3\]\[I_T = 2 + 1 + 0.67\]\[I_T = 3.67\text{A}\]

For a freely falling body starting from rest (\( u = 0 \)), we use the second equation of motion:\[ s = ut + \frac{1}{2}gt^{2} \]Since \( u = 0 \):\[ s = \frac{1}{2}gt^{2} \]\[ 20 = \frac{1}{2} \times 10 \times t^{2} \]\[ 20 = 5t^{2} \]\[ t^{2} = 4 \implies t = 2\text{s} \]

Mechanical waves require a material medium (solid, liquid, or gas) to propagate. Sound waves, water waves, and waves in pipes all need a medium. Radio waves are part of the electromagnetic spectrum; they consist of oscillating electric and magnetic fields and can travel through a vacuum.

The Velocity Ratio (V.R.) of an inclined plane is the ratio of the distance moved by the effort to the distance moved by the load. If the plane has a length \( L \) and height \( h \), then \( V.R. = L/h \).
From trigonometry, \( \sin \theta = h/L \).
Therefore, \( V.R. = \frac{1}{\sin \theta} \).

This problem follows Boyle's Law, which states that for a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume.
The formula is:\[ P_1 V_1 = P_2 V_2 \]Given:
\( P_1 = 400 \text{ cmHg} \)
\( V_1 = 10 \text{ cm}^3 \)
\( P_2 = 200 \text{ cmHg} \)

Calculation:\[ 400 \times 10 = 200 \times V_2 \]\[ 4000 = 200 V_2 \]\[ V_2 = \frac{4000}{200} = 20 \text{ cm}^3 \]

In standard atomic notation \( ^{A}_{Z}X \):
1. Z (Atomic Number) = Number of protons. In a neutral atom, this equals the number of electrons. Here, \( Z = 28 \).
2. A (Mass Number) = Protons + Neutrons. Here, \( A = 28 + 30 = 58 \).

Therefore, the correct representation is \( ^{58}_{28}X \).

All the statements describe fundamental aspects of electrostatics and current electricity.
* A: An object becomes positively charged by losing electrons (deficit).
* B: An object becomes negatively charged by gaining electrons (excess).
* C: In conductors, electric current is specifically the flow of charge carriers, which are typically free electrons.
Since all are correct, the answer is D.

Statement A is incorrect. A negative charge is created by an excess of electrons, not a deficit. A deficit of electrons results in a positive charge. Since the question asks for the statement that is *not* true, A is the correct choice.