Which has a higher resistance: a 50 W -220 V lamp or a 25 W – 220 V lamp? Calculate the ratio of resistances.
Answers
Explanation:
P= VI = V²/R
a) R = V²/P
= 220*220/50
= 44*22 = 968 ohm
b) R = 220*220/25
= 88*22 = 1936 ohm
in case b , resistance is higher than a .
Ratio of their resistance
= 968 : 1936
= 1 : 2
Answer:
Explanation:
In Current and Resistance, we described the term ‘resistance’ and explained the basic design of a resistor. Basically, a resistor limits the flow of charge in a circuit and is an ohmic device where V=IR. Most circuits have more than one resistor. If several resistors are connected together and connected to a battery, the current supplied by the battery depends on the equivalent resistance of the circuit.
The equivalent resistance of a combination of resistors depends on both their individual values and how they are connected. The simplest combinations of resistors are series and parallel connections ((Figure)). In a series circuit, the output current of the first resistor flows into the input of the second resistor; therefore, the current is the same in each resistor. In a parallel circuit, all of the resistor leads on one side of the resistors are connected together and all the leads on the other side are connected together. In the case of a parallel configuration, each resistor has the same potential drop across it, and the currents through each resistor may be different, depending on the resistor. The sum of the individual currents equals the current that flows into the parallel connections.
(a) For a series connection of resistors, the current is the same in each resistor. (b) For a parallel connection of resistors, the voltage is the same across each resistor.
