Physics Questions & Answers - Free Online Practice

2,366.

A stand-by generator is connected to fifteen 40 W lamps and musician's 600 W amplifying system. How much energy is used if the generator runs for 6 hours?

3.84k Wh

7.20k Wh

8.40k Wh

12.00k Wh

14.56k Wh

View answer & explanation

Correct answer is B

Total power = (15 x 40) + 600

= 1200 watts

Energy(kWh) = \(\frac{1200}{1000}\) x 6

= 7.2 kwH

2,367.

A quantity of sungas at -133 occupies 1/3m³ under pressure 1.4 x 10⁵ Nm^-2. if the gas occupies 31 m^-2 at 37^oC, its pressure will be

1.26 x 10³Nm^-2

3.3 x10⁴Nm^-2

1.35 x 10⁴Nm^-2

2.2 x 10⁴Nm^-2

10⁵Nm^-2

View answer & explanation

Correct answer is B

\(\frac{P_1V_1}{T_1}\) = \(\frac{P_2V_2}{T_2}\)

= \(\frac{\frac{1}{3} \times 1.4 \times 10^5}{-133 + 273}\) = \(\frac{P_2\times31}{37 +273}\)

P₂ = 3.3 x 10

2,368.

If the magnification of a virtual image formed of an object 10cm from a convex lens is 3, then the focal length of the lens is

10cm

15cm

16cm

19cm

20cm

View answer & explanation

Correct answer is B

V = 3u, U = 10cm

therefore U = -ve,

F = \(\frac{UV}{U + V}\)

= \(\frac{10 \times (-30)}{10 - 30 }\)

= 15cm

2,369.

What is the relative permitivity of a capacitor if its capacitance with a medium as dielectric is 16 farads and its capacitance with vacuum as dielectric is 2 farads?

\(\frac{1}{2}\)

View answer & explanation

Correct answer is D

E = E_r x E₀

16 = E_r x 2

E_r = 8

2,370.

Which of the following statements on the use of X-rays is incorrect? X-rays are used

in hospitals to obtain photogaphs of tissues and bones in the body

for the treatment of malignant growths like cancer cells

in detecting fingerprints

to reveal hidden flaws in metal castings and welded joints

to detect alternations which have been made to works of art

View answer & explanation

Correct answer is C

-The radiography of cultural objects is the use of radiography to understand intrinsic details about objects. Most commonly this involves X-rays of paintings to reveal underdrawing, pentimenti alterations in the course of painting or by later restorers, and sometimes previous paintings on the support.

-Hard X-rays are used for destroying cancerous cells

-Soft X-rays are used in medicine to photograph human parts

-. In the present work, the spatial elemental imaging capabilities of micro-X-ray fluorescence (MXRF) were used to visualize fingerprint patterns based on inorganic elements present in the prints.

However; Cobalt-60 is widely used in industrial radiography for the rapid checking of faults in wields and castings.