A. r/3

B. 3r

C. r/4

D. 4r

In Potentiometer experiment,the balancing length with a cell in the secondary circuit is found to be 480cm.when a resistor of 8 ohm is connected in parallel to the cell the balancing length is found to be 420cm.The internal resistance of the cell is

Three unequal resistors in parallel are equivalent to a resistance 1 ohm. If two of them are in the ratio 1:2and if no resistance value is fractional the largest of the three resistances in ohms is

One junction of thermo couple is at 0^{0}C and the other junction is heated .Maximum current in the thermo couple is observed when hot junction is at 240^{0}C.The temperature of the hot junction at which the direction of current reverses is

A cell of emf 2V and negligible resistance is connected in series with a resistance of 5 ohm,and a potentiometer wire of resistance 10 ohm.what is the potential drop per cm if the length of the potentiometer wire is 10m.The emf of a cell which is balanced by 750cm long wire is

A galvanometer of resistance 100Ω gives full scale deflection with 5mA current.To convert it into a 5 volt range voltmeter,the value of resistance connected in series is