NECO Past Questions and Answers - Page 226

1,126.

The space surrounding a magnet in which the magnetic force is exerted is

A.

magnetic field

B.

magnetic flux

C.

magnetic point

D.

magnetic pole

E.

magnetic strength

Correct answer is A

No explanation has been provided for this answer.

1,127.

Which of the following statements about the concept of solid friction is NOT true?

A.

It always acts in the direction of motion

B.

It causes wear and tear in car tyres

C.

It depends on the nature of the surfaces in contact

D.

It is independent of the area of the surfaces in contact.

E.

It reduces the efficiency of the machine

Correct answer is A

No explanation has been provided for this answer.

1,128.

In 90 seconds, the mass of a radioactive element reduces to \(\frac{1}{16}\) of its original value. Determine the half- life of the element.

A.

15.0s

B.

18.0s

C.

22.5s

D.

30.0s

E.

45.0s

Correct answer is C

\(\frac{1}{16} = (\frac{1}{2})^n\)

\((\frac{1}{2})^4 = (\frac{1}{2})^n\)

\(n = 4\)

90 secs = 4 half lives

1 half life = \(\frac{90}{4}\) secs

= 22.5 secs

1,130.

A transformer is required to give 120V from a 240V mains supply. If the primary has 5500 turns, how many turns has the secondary?

A.

232

B.

450

C.

550

D.

2750

E.

11000

Correct answer is D

No explanation has been provided for this answer.