Advertisements
Advertisements
प्रश्न
A resistor has a resistance of 176 ohms. How many of these resistors should be connected in parallel so that their combination draws a current of 5 amperes from a 220 volt supply line?
Advertisements
उत्तर
Suppose x resistors should be connected in parallel to draw a current of 5 A.
For a parallel combination, 1 / R = 1 / R1 + 1 / R2 + 1 / R3 + ... (x times)
Here, R1 = R2 = R3 = ... = 176 Ω
Then the resultant resistance, R = 176 / x Ω
Given that the current, I = 5 A and voltage, V = 220 V
Then by Ohm's law, V = IR
By substituting the values, we get:
`220=5xx176/x`
x = 4
Hence, four resistors of 176 Ω each should be connected in parallel to draw a current of 5 A from a 220 V supply line.
APPEARS IN
संबंधित प्रश्न
With a neat labelled diagram and derive the equation for three resistances connected in parallel.
An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?
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
An electric heater which is connected to a 220 V supply line has two resistance coils A and B of 24 Ω resistance each. These coils can be used separately (one at a time), in series or in parallel. Calculate the current drawn when:
(a) only one coil A is used.
(b) coils A and B are used in series.
(c) coils A and B are uses in parallel.
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.
In parallel combination of resistances ______.
Five resistors, each 3 Ω, are connected as shown in Fig. Calculate the resistance
- between the points P and Q.
- between the points X and Y.
A particular resistance wire has a resistance of 3 ohm per meter. Find the total resistance of three lengths of this wire each 1.5 m long, joined in parallel.
A uniform wire with a resistance of 27 Ω is divided into three equal pieces and then they are joined in parallel. Find the equivalent resistance of the parallel combination.
An electrical appliance has a rating 100 W, 120V. The resistance of element of appliance when in use:
How does the resistance of a metallic wire depend on the length of wire?
How does the resistance of a metallic wire depend on the thickness of wire?
Two resistors when connected in parallel give the resultant resistance of 2 ohms, but when connected in series the effective resistance becomes 9 ohms. Calculate the value of each resistance.
The least resistance obtained by using 2 Ω, 4 Ω, 1 Ω and 100 Ω is:
Assertion: When a battery is short circuited, the terminal voltage is zero.
Reason: In a short circuit, the current is zero.
Three resistors of 6Ω, 4Ω and 4Ω are connected together so that the total resistance is 8Ω. Draw a diagram to show this arrangement and give reason to justify your answer.
Two V-I graphs A and B for series and parallel combinations of two resistors are as shown. Giving reason state which graph shows (a) series, (b) parallel combination of the resistors.
Study the following circuit:
On the basis of this circuit, answer the following questions:
i. Find the value of total resistance between the points A and B.
ii. Find the resistance between the points B and C.
iii. Calculate the current drawn from the battery, when the key is closed
OR
iii. In the above circuit, the 16Ω resistor or the parallel combination of two resistors of 8 Ω, which one of the two will have more potential difference across its two ends? Justify your answer.
Four resistors each of resistance 5 Ω are connected in parallel. What is the effective resistance?
