Electrical Engineering - Energy and Power - Discussion

The exact answer is 1W.

1.2W resistor rating b/w above 1W below 1.5W/2W.

1W resistor is will use instead of 1.2W resistor will heatup. So we can use a 2W resistor instead of 1.2W. Rating will high no problem for ckt but rating will less than operating value equipment will burn.

If equipment handles the 1.2 w then it's rated value should be greater than 1.2 w and nearest also other wise more losses will occur.

It is an assumption that the source is reliable if it can supply 70% of its own power rating & 30% of power is required to energies itself.

CONCEPT FOR THE SELECTION OF THE EQUIPMENT RATING.

Basically in case of the selection of the switchgear:

1) First in case of the selection of switch the rating at least 2.5 times of the rated current in case of continuous duty cycle.

2) Secondly the selection of switchgear like MCB, MCCB, ELCB, RCCB depends on the type of load selection i.e. in case of induction motor the starting current is high in that case the rating of switchgear is some higher than the starting current otherwise the mcb trip the circuit.

3) In case other than the induction load the rating is 2.5 times of the load current.

Only 2watt resistor is handle 1.2 watt because it was a nearest resistor for handle it.

So what is answer and why?

To handle 1.2 W, it should be of a slightly higher rating. If we choose a very high rating, cost increases. So it is advisable to choose a slightly higher rating of resistors.

Carbon resistors, for example, are commonly made in wattage ratings of 1/8 (0.125) W, 1/4 (0.250) W, 1/2 (0.5) W, 1W, and 2 Watts. Generally speaking the larger their physical size the higher its wattage rating. However, it is always better to select a particular size resistor that is capable of dissipating two or more times the calculated power.

What is carbon composition resistor?