Can we determine voltage drop across each of series connected 200w bulb and 300w heater if i/p voltage is 200v?

Question

series connected 200w bulb and 300w heater if i/p voltage is 200v so can we determine voltage drop across each.and what if we change the input voltage to 100 v again can we find out resistances
Que..
a 100 w bulb is connected in series with a room heater. if now 100 w bulb is replaced by a 40 w bulb, the heater o/p will be
1)increase 2)decrease 3)remain same 4)uncertain

Answer 1

Strangely enough, I would say (B) decreases.



This is because a 40W bulb has a higher resistance than a 100W bulb.

Remember that Watts = V^2 / R

So if we have a fixed voltage (power supply of 220Vac), then a lower wattage is produced when R is higher.



Here's what happens with the heater in series -

lets say 100W bulb resistance is R-100 & 40W is R-40 & heater is R-heater



Voltage across heater with 100w bulb is -- V x [ R-heater / ( R-heater + R-100 ) ]

and with 40W bulb -- V x [ R-heater / ( R-heater + R-40 ) ]



Since the 2nd equation is a smaller value ( R-40 is larger than R-100), hence voltage across heater drops & there is less output.

Answer 2

here wattage rating is based on 220V AC. on this basis resistance of each circuit is 242 Ohms and 161 Ohms.

total circuit resistance is 403 Ohms.

when 200V is applied on the total load i.e. on 403 Ohms , current flow in this circuit will be 0.495 Amps.



Voltage drop (IR drop) of each device will be 120V and 80 V when you apply 200v across this loads.



Your second question when a hundred watts bulb is replaced by 40W bulb it means overall resistance of the circuit is increased. in the series circuit. that will cause low power output from heater. Hope now it is solved

Answer 3

Surely if they are series connected, the answer depends entirely on the resistances of the 2 components, which arent given... i mean, you can assume that the watt rating is based on 230V AC or whatever, dropped directly acorss it, and work out a resistance, but that isnt specified in the question so you cant really get an answer....

Answer 4

If the three resistors are related in sequence, then Re = equivalent resistance = 3R and utilising Ohm's regulation, the present interior the circuit is I = 60/3R I = 20/R Voltage drop for the period of each and each resistor = (20/R)(R) = 20 volts wish this enables.