NECO Physics Past Questions & Answers - Page 55

271.

A 220 V, 60 Hz alternating current supply is connected to an inductor of 3.5H. What is the current passing through the inductor?

A.

0.0167 A

B.

0.1670 A

C.

1.6700 A

D.

16.7000 A

E.

167.0000 A

Correct answer is B

No explanation has been provided for this answer.

273.

Which statement is a correct consequence of the uncertainly principle?

A.

A particle’s kinetic energy cannot be measured accurately at any time

B.

Both momemtum and energy of a particle can be known with absolute certainly

C.

It is possible to measure exactly both the position and momentum of a particle at the same time

D.

The complete knowledge of the position of a particle implies the complete ignorance of its energy

E.

The uncertainty in our knowledge of energy and the duration taken to measure it, are each less than Planck’s constant.

Correct answer is A

The Heisenberg uncertainty principle states that it is impossible to make precise measurements of both the position and momentum of a particle simultaneously

274.

A cell can supply currents of 0.60 A and 0.30 A through a 2.0 ω and a 5.0 ω resistor respectively. What is the internal resistance of the cell?

A.

0.2 ω

B.

0.4 ω

C.

1.0 ω

D.

3.0 ω

E.

9.0 ω

Correct answer is C

No explanation has been provided for this answer.

275.

Which material is best for making a permanent magnet?

A.

Aluminum

B.

cobalt

C.

copper

D.

soft iron

E.

steel

Correct answer is E

Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite

Permanent magnets are made from special alloys (ferromagnetic materials) such as iron, nickel and cobalt, several alloys of rare-earth metals and minerals such as lodestone.

When a nonmagnetic piece of steel is applied to a magnet, the atoms within it rearrange themselves in a manner that creates a permanent magnet.