Give reasons for the following:
If you connect ammeter in parallel it burns

Give reasons for the following: If there is a glass door and is closed then you may not be able to see it and get hurt if you try to paas through it.

Give reason for the following: Hydrogen burns with a pop sound in air.

Give suitable reasons for the following statements: We feel burning sensation in the stomach when we over eat.

Read the following text and answer the following questions on the basis of the same: Shunt resistance: The ammeter shunt is the device which provides the low resistance path to the flow of current. It is connected in parallel with the ammeter. In some ammeter the shunt is in-built inside the instrument while in others it is externally connected to the circuit. Manganin and Constantan are used for making the shunt of DC and AC ammeter respectively. Ammeters are designed for measurement of low current. For measuring high current, the shunt is connected in parallel to the ammeter. The significant portion of the current passes to the shunt because of the low resistance path and little amount of current passes through the ammeter. The shunt is connected in parallel to the ammeter because of which the voltage drops across the meter and shunt remain the same. Thus, the movement of the pointer is not affected by the shunt. Let us consider that the current to be measured is I. The circuit has ammeter and shunt connected parallel to each other. The ammeter is designed for measurement of small current say, I_(m) . The magnitude of the current I passes through the meter is very high, and it will burn the meter. So, for measuring the current I the shunt is required in the circuit. As the shunt connects in parallel with the ammeter, thus the same voltage drops occur between them: I_(Sh)R_(SH)=I_(m)R_(m) :.R_(SH)=I_(m)R_(m)//I_(SH) Shunt current I_(SH)=I-I_(m) So, R_(SH)=I_(m)R_(m)//(I-I_(m)) :.I//I_(m)=1+(R_(m)//R_(SH)) The ratio of the total current to the current required for the movement of the ammeter coil is called the multiplying power of the shunt. :. The multiplying power =m=I//L_(m) R_(SH)=R_(m)//(m-1) The following are the requirements of the shunt. • The resistance of the shunt should remain constant with time. • The temperature of the material-should remain same even though substantial current flows through the circuit. Materials used for making shunt of DC and AC ammeter are respectively

Give reason of you feel cool when you touch a piece of ice.

Two exactly similar heating resistances are connected (i) in series, and (ii) in parallel, in two different circuits, one by one. If the same current is passed through both the combinations, is more heat obtained per minute when they are connected in series or when they are connected in parallel? Give reason for you answer.

An ammeter has a resistance R and a range I. To increase its range to nL, the resistance that should be connected in parallel with it, is given by