Physics: Need answers for questions regarding topic 'ENERGY'

[Shizza Jalil]

So these are questions from May/June 2012, I can't find the mark scheme, so could use your help. Please do answer.

(a) The principle of conservation of energy states that energy can neither be created nor destroyed.
What, then, does happen to the energy supplied to a device such as a motor or a television? (1)

(b) The television is switched on to watch a programme. During this time, 720 kJ of electrical energy is supplied. (Diagram shows total electrical energy input = 720 kJ, light energy output = 4 kJ and sound energy output = 20 kJ)

(i) From the information given, find the total energy provided for the viewer to see and hear the television during the programme. (1)
(ii) Suggest what happens to the rest of the energy supplied. (2)
(iii) Calculate how much energy is involved in (b)(ii). (1)
(iv) Comment on the efficiency of the television. (1)


Please do reply, I'd be very grateful.

 

[Mahad Khan]

Are you sure this is the whole question? Can you give me the link to this paper as you have not mentioned which paper and which variant this is.

 

[DarkEclipse]

(a) The principle of conservation of energy states that energy can neither be created nor destroyed.
What, then, does happen to the energy supplied to a device such as a motor or a television? (1)
Ans. The amount of energy remains the same, it simply gets converted to another form.

(b) The television is switched on to watch a programme. During this time, 720 kJ of electrical energy is supplied. (Diagram shows total electrical energy input = 720 kJ, light energy output = 4 kJ and sound energy output = 20 kJ)
(i) From the information given, find the total energy provided for the viewer to see and hear the television during the programme. (1)
Ans. 20kJ sound energy+4kJ light energy =24kJ.
Therefore, 24kJ is provided for the viewer to see and hear the television during the programme.

(ii) Suggest what happens to the rest of the energy supplied. (2)
Ans. The rest of the energy is converted and wasted as thermal/heat energy.

(iii) Calculate how much energy is involved in (b)(ii). (1)
Ans. 20kJ+4kJ=24kJ
720kJ-24kJ=696kJ
Therefore, the energy involved is 696kJ.

(iv) Comment on the efficiency of the television. (1)
Ans. The idea is not very good as the efficiency is low and too much energy is consumed.


Hope I helped

 

[Shizza Jalil]

Thank you, DarkEclipse.

 

[DarkEclipse]

Thank you, DarkEclipse.

No problem, happy to help

 

[Shizza Jalil]

Much appreciated.

 

[DarkEclipse]