Advertisements
Advertisements
Question
An electronics hobbyist is building a radio which requires 150 Ω in her circuit, but she has only 220 Ω, 79 Ω, and 92 Ω resistors available. How can she connect the available resistors to get the desired value of resistance?
Advertisements
Solution
Available resistances = 220 Ω, 79 Ω 92 Ω
Case I:
If 3 resistors are connected in series, then
RS = R1 + R2 + R3 = 220 + 79 + 92 = 391
This value is greater than the required resistance so it is not possible.
Case II:
If 3 resistors are connected in parallel, then
`1/"R"_"p" = 1/"R"_1 + 1/"R"_2 + 1/"R"_3`
`1/"R"_"p" = 1/220 + 1/79 + 1/92` = 0.0279
Rp = 35.84 This does not meet the requirement.
Case III:
If R1 and R2 are connected in parallel and R3 in series
`1/"R"_"p" = 1/"R"_1 + 1/"R"_2 = 1/220 + 1/79 = 0.0172`
`=> "R"_"p" = 58.14 Omega`
This meets the requirement.
APPEARS IN
RELATED QUESTIONS
If the potential difference across the ends of a conductor is 220 V and the resistance of the conductor is 44 Ω (ohm), then the current flowing through is _________.
- 0.2 A
- 0.5 A
- 2 A
- 5 A
The relationship between the potential difference and the current in a conductor is stated in the form of a law.
1) Name the law.
2) What does the slope of V-I graph for a conductor represent?
3) Name the material used for making the connecting wire.
Find the expression for the resistivity of a material and state the SI unit of resistivity.
Four resistances of 16 ohms each are connected in parallel. Four such combinations are connected in series. What is the total resistance?
How much energy is consumed when a current of 5 amperes flows through the filament (or element) of a heater having resistance of 100 ohms for two hours? Express it in joules.
In a conductor 6.25 × `10^16` electrons flow from its end A to B in 2 s. Find the current flowing through the conductor (e = 1.6 × `10^-19` C)
In the circuit shown below in Fig, calculate the value of x if the equivalent resistance between A and B is 4 Ω.
The filament of a bulb takes a current 100 mA when potential difference across it is 0.2 V. When the potential difference across it becomes 1.0 V, the current becomes 400 mA. Calculate the resistance of filament in each case and account for the difference.
Explain the equivalent resistance of a parallel resistor network.
The voltage - current readings of a certain material are shown in the table given below:
| Voltage (V) | 10 V | 20 V | 30 V |
| Current (I) | 2 A | 3 A | 4 A |
Study the table.
- State whether the conductor used is ohmic or non-ohmic.
- Justify your answer.
- State Ohm's law.
