2001 - JAMB Physics Past Questions and Answers - page 4

The sun produces energy through nuclear fusion. * **Nuclear fusion:** This process involves the combination of lighter atomic nuclei, such as hydrogen, to form a heavier nucleus, such as helium. This process releases a tremendous amount of energy. * **Nuclear fission:** This involves the splitting of a heavy nucleus into lighter nuclei, also releasing energy but is not the primary energy source of the sun. * **Electron collision:** While electrons are involved in various atomic processes, electron collisions are not the primary energy-producing mechanism in the sun. * **Radioactive decay:** Radioactive decay is the process by which an unstable nucleus loses energy, but it is not the primary source of energy generation in the sun.

At resonance in an AC circuit, the inductive reactance (XL) equals the capacitive reactance (XC). This results in the impedance of the circuit being purely resistive. Since the voltage and current are in phase in a purely resistive circuit, the phase angle is 0°.

The force on a current-carrying conductor in a magnetic field is given by the equation: F = B I L sin(θ) where: * F is the force * B is the magnetic field strength * I is the current * L is the length of the conductor * θ is the angle between the conductor and the magnetic field The force is greatest when sin(θ) is at its maximum value, which is 1. This occurs when θ = 90°, meaning the conductor is at a right angle with the field.

A transistor functions primarily as a switch (controlling the flow of current) and an amplifier (increasing the strength of a signal).

Eddy currents are unwanted circulating currents induced in a conductor when the conductor experiences a changing magnetic field. These currents cause energy losses in the form of heat. To reduce these losses: * **Insulated soft iron wires:** Using insulated soft iron wires creates a laminated core. This lamination increases the resistance to the flow of eddy currents, thus reducing their magnitude and the associated energy losses. * **Low resistance wires and High resistance wires:** The resistance of the wire isn't the primary factor to reduce the energy loss. * **Few turns of wires:** The number of turns isn't the primary factor to reduce the energy loss.

Here's how to solve this problem: 1. **Recall the resonance frequency formula:** The resonance frequency (f) of an LC circuit is given by: f = 1 / (2π * sqrt(L * C)) where: * f is the resonant frequency in Hertz (Hz) * L is the inductance in Henries (H) * C is the capacitance in Farads (F) 2. **Convert the given frequency to Hz:** The frequency is given as 200 kHz, which is equal to 200,000 Hz. 3. **Plug in the known values and solve for L:** * f = 200,000 Hz

The magnetic force on a charge is given by
F = qVB Sinθ,
thus the force is proportional to both the magnitude by the charge (q) and the velocity (V)
(i/e F α qV)

The pendulum that will resonate with P is T. being of the same length and therefore of the same frequency.

Since the number of pulleys present is 6, it implies that the velocity ratio VR = 6

∴ efficiency =	M.A	x 100 1
V.R

= Load/Effort x 1/V.R x 100/1
= ²⁴⁰/₈₀ x ¹/₆ x ¹⁰⁰/₁
= 50%
∴ Efficiency = 50%

Snell's law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the refractive index of the medium. Here's the breakdown: 1. **Angle of incidence (α):** The angle between the incident ray and the normal. 2. **Angle of refraction (β):** The angle between the refracted ray and the normal. 3. **Refractive index (n):** n = sin(α) / sin(β)