Advertisements
Advertisements
Question
Which of the following arrangement, A or B, has the lower combined resistance?
Advertisements
Solution
In figure A, the resistance, RA = 10 Ω
In figure B, the resistors of 10 Ω and 1000 Ω are connected in parallel combination.
Therefore:
`1/R=1/R_1+1/R_2`
`1/R=1/10+1/1000`
or `1/R=100/1000+1/1000`
or`1/R=101/1000`
`R=1000/101=9.9`Ω
RB = 9.9 Ω
So, the arrangement B has lower resistance.
APPEARS IN
RELATED QUESTIONS
With a neat labelled diagram and derive the equation for three resistances connected in parallel.
Several electric bulbs designed to be used on a 220 V electric supply line are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistances, which may be used separately, in series, or in parallel. What are the currents in the three cases?
Show how would you join three resistors, each of resistance 9 Ω so that the equivalent resistance of the combination is
1) 13.5
2) 6 Ω
State the law of combination of resistances in parallel.
A wire that has resistance R is cut into two equal pieces. The two parts are joined in parallel. What is the resistance of the combination?
Find the current in each resistor in the circuit shown below:
Two resistors, with resistance 5 Ω and 10 Ω respectively are to be connected to a battery of emf 6 V so as to obtain:
(i) minimum current flowing
(ii) maximum current flowing
(a) How will you connect the resistances in each case?
(b) Calculate the strength of the total current in the circuit in the two cases.
In the circuit given below:
(a) What is the combined resistance?
(b) What is the p.d. across the combined resistor?
(c) What is the p.d. across the 3 Ω resistor?
(d) What is the current in the 3 Ω resistor?
(e) What is the current in the 6 Ω resistor?
In the diagram shown below, the cell and the ammeter both have negligible resistance. The resistor are identical.
Two resistances when connected in parallel give resultant value of 2 ohm; when connected in series the value becomes 9 ohm. Calculate the value of each resistance.
Are the lights in your house wired in series?
If current flows through two lamps arranged:
(a) in series,
(b) in parallel,
and the filament of one lamps breaks, what happens to the other lamp? Explain your answer.
A cell supplies a current of 1.2 A through two 2Ω resistors connected in parallel. When the resistors are connected in series, if supplies a current of 0.4 A. Calculate the internal resistance and e.m.f of the cell.
The equivalent resistance of a parallel combination of two resistors of 30 Ω and 60 Ω is ______________.
How does the resistance of a metallic wire depend on the thickness of wire?
Two resistors having resistance 8 Ω and 12 Ω are connected in parallel. Find their equivalent resistance.
You have three resistors of values 2 Ω, 3 Ω, and 5 Ω. How will you join them so that the total resistance is less than 1 Ω? Draw a diagram and find the total resistance.
