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Question

Two \(100\ \Omega\) resistors are connected in parallel, and this combination is connected across a 40-V supply. Find the current supplied by the voltage source.

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is
0.8 A

Parallel Resistor Current Calculation

The problem asks for the total current supplied by the voltage source when two resistors are connected in parallel across it.

Identify Given Values

  • Resistance of each resistor, \(R_1 = R_2 = 100\ \Omega\).
  • Voltage supply, \(V = 40\ V\).

Calculate Equivalent Resistance

For resistors in parallel, the equivalent resistance (\(R_{eq}\)) is calculated using the formula:

\( \frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} \)

Substituting the values:

\( \frac{1}{R_{eq}} = \frac{1}{100\ \Omega} + \frac{1}{100\ \Omega} = \frac{2}{100\ \Omega} \)

Therefore, the equivalent resistance is:

\( R_{eq} = \frac{100\ \Omega}{2} = 50\ \Omega \)

Calculate Total Current

Using Ohm's Law, the total current (\(I\)) supplied by the voltage source is:

\( I = \frac{V}{R_{eq}} \)

Substituting the values:

\( I = \frac{40\ V}{50\ \Omega} \)

\( I = 0.8\ A \)

Conclusion

The current supplied by the voltage source is 0.8 A.

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Important Questions from Combination of Resistors — Series and Parallel

  1. Consider two resistors, $R_1$ and $R_2$, connected in series to a DC voltage source. Which of the following statements accurately describes the distribution of current and voltage across these resistors?

  2. A cell of negligible resistance and e.m.f 2 volt is connected to series combination of 2 ohm, 3 ohm and 5 ohm. The potential difference across the 3 ohm resistance is:

  3. Two bulbs A, of (100w, 100v), and B of (60 w, 100v) are connected in series and across the series combination 200 v is applied. Which bulb will be fused?

  4. 3 resistors of 3 ohm each connected in series. What is the mean values of resistors?

  5. The equivalent resistance of the resistances (two) joined in parallel is 6/5 Ω. When one of the resistance wire is broken, the effective resistance becomes 2Ω. The resistance of the wire that got broken was :

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