# Master Physics with Ease: Access JAMB, WAEC, NECO and Post UTME Past Questions Today!

Question 1: When two magnets are used to magnetize a soft iron bar PQ as shown in the diagram, what are the correct polarities at points P and Q?

#### Question can be turned as

What are the correct polarities at points P and Q when using two magnets to magnetize a soft iron bar PQ?

Option A) S and N Option B) N and N Option C) S and S Option D) N and S

Answer: Option D) N and S

Explanation: The north pole of one magnet should be placed near the south pole of the other magnet, and vice versa, when using two magnets to magnetize a soft iron bar. This creates a magnetic field in the iron bar with a north pole at point P and a south pole at point Q.

Question 2: Why are keepers used in storing magnets?

#### Question can be turned as

What is the purpose of keepers in storing magnets?

Option A) To reduce self-demagnetization Option B) To cancel the effect of the Earth’s magnetic field Option C) To protect the magnet from stray electric fields Option D) To increase the strength of the magnets

Answer: Option A) To reduce self-demagnetization

Explanation: Keepers are used to reduce self-demagnetization, which occurs when a magnet is not in use and its magnetic domains become disordered, causing it to lose its magnetism. A keeper is a piece of soft iron that is placed across the poles of a magnet to provide a closed magnetic circuit and keep the domains in alignment.

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Question 3: A charge of 10μC moves with a velocity of 1.0×105ms−1 at right angles to a uniform magnetic field of flux density 5.0×10−4T. What is the force acting on the charge?

#### Question can be turned as

Option A) 5.0×10−5N Option B) 5.0×10−4N Option C) 5.0×105N Option D) 5.0×106N

Explanation: The force acting on a charge moving at right angles to a magnetic field is given by the equation F = Bqv, where B is the magnetic field strength, q is the charge, and v is the velocity of the charge. Substituting the given values, we get F = (5.0×10−4T)(10μC)(1.0×105ms−1) = 5.0×10−4N.

Question 4: Which of the following statements about steel and soft iron is incorrect?

#### Question can be turned as

Option A) Steel is more magnetized than soft iron.

and Option B) Permanent magnets are usually made of steel.

Option C) Soft iron is more readily magnetized than steel.

Option D) Soft iron more readily loses its magnetism than steel.

Answer: Option A) Steel is more magnetized than soft iron.

Explanation: Steel is less magnetizable than soft iron, which means it is harder to magnetize and demagnetize. Permanent magnets are often made of alloys of iron, cobalt, and nickel, but not steel.

1. What determines the polarity at the ends of an electromagnet?

The polarity at the ends of an electromagnet is determined by the direction of current flowing through the wire. As the current flows, it creates a magnetic field around the wire, and the direction of the field depends on the direction of the current.

Option A: magnitude of the current passing through the wire Option B: material of the core of the magnet Option C: material of the coil

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#### The question can also be written as

What determines the polarity of an electromagnet? The polarity is determined by the direction of the current passing through the wire. The magnetic field created by the current flow around the wire determines the direction of the polarity. The material of the core of the magnet or the coil does not affect the polarity.

1. How many beta particles are emitted in the radioactive decay of 198Au?

The radioactive decay of 198Au results in the emission of one beta particle.

Option A: 1 Option B: 2 Option C: 3 Option D: 5

#### The question can also be written as

1. What is the phenomenon of two light atomic nuclei combining to form a heavy nuclide called?

The phenomenon of two light atomic nuclei combining to form a heavy nuclide with the release of energy is called nuclear fusion.

Option A: radioactivity Option B: nuclear fusion Option C: nuclear fission Option D: chain reaction

#### The question can also be written as

1. In a p-type semiconductor, what is the majority charge carrier?

In a p-type semiconductor, the majority charge carrier is the hole.

Option A: number of holes is equal to the number of electrons Option B: electrical resistivity increases Option C: electrons are the majority charge carriers Option D: holes are the majority charge carriers

#### The question can also be written as

What is the majority charge carrier in a p-type semiconductor? In a p-type semiconductor, the majority charge carrier is the hole, and not the electron.

1. What is the uncertainty principle relation given as?

The uncertainty principle relation is given as Δx . Δp ≥ h, where Δx is the uncertainty in position measurement and Δp is the uncertainty in momentum measurement.

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Option A: Δx . Δp = h Option

B: Δx . Δp ≤ h Option

C: Option Δx . Δp ≥ h Option

D: Δx . Δp > h

#### The question can also be written as

1. What is the gravitational attraction between two objects of masses 80kg and 50kg separated by a distance of 0.2m, if the gravitational constant is 6.6 x 10^-11Nm kg?

The gravitational attraction between the two objects is 1.3 x 10^-6 N.

Option A: 4.9 × 10^-9 N Option B: 1.3 × 10^-6 N Option C: 6.6 × 10^-8 N Option D: 6.6 × 10^-6 N Option E: 2.6 × 10^-9 N

#### The question can also be written as

Calculate the gravitational attraction between two objects of masses 80kg and 50kg separated by a distance of 0.2m,