Advertisements
Advertisements
प्रश्न
Two resistances X and Y are connected turn by turn:
- in parallel, and
- in series.
In which case the resultant resistance will be less than either of the individual resistances?
Advertisements
उत्तर
When two resistances, x and y, are connected:
i. In parallel:
The resultant resistance is given by:
`1/R_p = 1/x + 1/y`
Rp = `(x y)/(x + y)`
Since Rp is the reciprocal of the sum of reciprocals, it is always less than either x or y individually (provided both x and y are positive).
ii. In series:
The resultant resistance is given by:
Rs = x + y
This is always greater than either x or y individually.
∴ The resultant resistance will be less than either of the individual resistances when the resistors are connected in parallel.
APPEARS IN
संबंधित प्रश्न
The substance having infinitely high electrical resistance is called:
(a) conductor
(b) resistor
(c) superconductor
(d) insulator
Give the law of combination of resistances in series.
If five resistances, each of value 0.2 ohm, are connected in series, what will be the resultant resistance?
The diagram below shows part of a circuit:
If this arrangement of three resistors was to be replaced by a single resistor, its resistance should be:
(a) 9 Ω
(b) 4 Ω
(c) 6 Ω
(d) 18 Ω
Three resistors of 6.0 Ω, 2.0 Ω and 4.0 Ω are joined to an ammeter A and a cell of emf 6.0 V as shown in the following figure. Calculate :
- the effective resistance of the circuit.
- the reading of ammeter.
What do you mean by power rating of an electrical appliance? How do you use it to calculate
(a) the resistance of the appliance and
(b) the safe limit of the current in it, while in use?
When do you say that the resistors are connected in this way? Draw a circuit diagram.
Answer the following question.
While studying the dependence of potential difference ( V) across a resistor on the current (I) passing through it, in order to determine the resistance of the resistor, a student took 5 readings for different values of current and plotted a graph between V and t. He got a straight line graph passing through the origin. What does the straight-line signify? Write the method of determining the resistance of the resister using this graph.
Bends in a rubber pipe reduce the flow of water through it. How would the bands in a wire affect its electric resistance?
What material is used for making wire to prepare heating coils? Give a reason.
Why are thick copper wires used as connecting wires?
Write an expression for the resistance of a conducting wire in terms of its length and area of cross-section.
How does the resistivity of a semiconductor depend on temperature?
How does the resistivity of an alloy such as constantace depends on temperature.
Define the term resistivity and state its S.I. unit. Which will have higher resistivity a conductor or an insulator.
Illustrate-combination of cells e.g., three cells, in series, explaining the combination briefly. Obtain an expression for current ‘i’ in the combination.
Two resistors having 2Ω and 3Ω resistance are connected—(i) in series, and (ii) in parallel. Find the equivalent resistance in each case.
If the current I through a resistor is increased by 100% (assume that temperature remains unchanged), the increase in power dissipated will be:
