Physics - Study Mode

[#506] Skating on ice is possible because
Correct Answer

(C) The pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water

Explanation

Solution: Skating on ice is possible because the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water.

[#507] If a copper wire is increased to double its length, its resistance will become
Correct Answer

(A) Four times

Explanation

Solution: When the wire is stretched to double the length , the area of cross section gets reduced to half. So when the wire is stretched, the resistance multiplies by four times.

[#508] The filament of electric bulb is made up of :
Correct Answer

(D) Tungsten

Explanation

Solution: The filament of an electric bulb is made of tungsten because it has some amazing properties including the highest melting point (3422 o C), lowest vapor pressure, and greatest tensile strength out of all the metals.

[#509] Two electric bulbs marked 25W – 220V and 100W – 220V are connected in series to a 440Vsupply. Which of the bulbs will fuse?
Correct Answer

(A) 25 W

Explanation

Solution: When connected in series, the voltages divide in them in the ratio of their resistances. The voltage of 440 V devides in such a way that voltage across 25 w bulb will be more than 220 V. Hence 25 w bulb will fuse.

[#510] 1 WH =
Correct Answer

(C) 3600 joules

Explanation

Solution: 1 WH (Watt hour) = 3600 joules