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Question

When two resistors of equal value are connected across a 220 V DC supply, the current through each resistor is 1 A. Find the colour code of the resistors.

The correct answer is

Red, Red, Brown

To solve the problem of finding the colour code of the resistors, we can follow these steps:

  1. First, determine the resistance of each resistor. According to Ohm's Law, \(\(V = IR\)\), where \(V\) is the voltage, \(I\) is the current, and \(R\) is the resistance.
  2. Since the resistors are of equal value, they can be considered as identical resistors connected in parallel across the voltage source. Given that when two equal resistors are connected in parallel, the voltage across each resistor is equal to the source voltage. 
    Thus, using Ohm’s Law for each resistor, we have: 
    \(V = I \times R\) 
    Given: \(V = 220 \, \text{V}\), \(I = 1 \, \text{A}\) 
    So, rearranging gives: 
    \(R = \frac{V}{I} = \frac{220 \, \text{V}}{1 \, \text{A}} = 220 \, \Omega\)
  3. Next, we need to determine the colour code for a \(220 \, \Omega\) resistor. The common colour code for resistors is as follows:
    1. 1st Band: Represents the first significant digit.
    2. 2nd Band: Represents the second significant digit.
    3. 3rd Band: Is a multiplier.
  4. For a resistance of \(220 \, \Omega\):
    • The first digit is '2' (Colour: Red)
    • The second digit is '2' (Colour: Red)
    • The multiplier value is \(10^1\) (Colour: Brown)
  5. Therefore, the colour code for a \(220 \, \Omega\) resistor is Red, Red, Brown.

Hence, the correct answer and colour code of the resistors is: Red, Red, Brown.

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Important Questions from Resistors

  1. Given the relationship $R = \rho \frac{L}{A}$, where $R$ represents electrical resistance, $L$ is the length of the material, and $A$ is its uniform cross-sectional area, what is the standard International System of Units (SI) unit for specific resistance ($\rho$)?
    Assume $R$ is measured in Ohms ($\Omega$), $L$ in meters ($m$), and $A$ in square meters ($m^2$).
  2. A wire of resistance R is connected to an EMF source E. The charge flowing through the resistor is time dependent as Q = at - bt2. The heat dissipated in the wire is:

  3. What is varistor?

  4. A voltage of 100 V is applied to a circuit of resistance of 20 Ohms, the Power dissipated by the resistance will be

  5. The resistance value of a carbon resistor having red, violet, orange and gold colour band is

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