Math Problem Statement

Concerning Figure 4.1, calculate the total resistance, total current, individual currents through each resistor, and power dissipated across the resistors using Ohm's law.

Solution

Let’s break this problem down step by step according to the instructions and the circuit diagram provided.

Given Information:

  • R3=360ΩR_3 = 360 \, \Omega
  • R4=360ΩR_4 = 360 \, \Omega
  • R5=470ΩR_5 = 470 \, \Omega
  • Voltage source E1=5VE_1 = 5 \, \text{V}

1. Connect a jumper between points A and D

This effectively creates a parallel circuit across R3R_3, R4R_4, and R5R_5.


2. Calculate the total resistance (RTR_T)

Since R3R_3, R4R_4, and R5R_5 are in parallel, the formula for the equivalent resistance is:

1RT=1R3+1R4+1R5\frac{1}{R_T} = \frac{1}{R_3} + \frac{1}{R_4} + \frac{1}{R_5}

Substitute the given values:

1RT=1360+1360+1470\frac{1}{R_T} = \frac{1}{360} + \frac{1}{360} + \frac{1}{470}

1RT=0.00278+0.00278+0.00213=0.00769\frac{1}{R_T} = 0.00278 + 0.00278 + 0.00213 = 0.00769

RT=10.00769130ΩR_T = \frac{1}{0.00769} \approx 130 \, \Omega


3. Calculate the total current (ITI_T)

The total current is calculated using Ohm’s law:

IT=E1RTI_T = \frac{E_1}{R_T}

IT=51300.0385A(38.5mA)I_T = \frac{5}{130} \approx 0.0385 \, \text{A} \, (38.5 \, \text{mA})


4. Calculate the currents through R3R_3, R4R_4, and R5R_5

For resistors in parallel, the current through each resistor is calculated individually using Ohm’s law:

IR=VRI_R = \frac{V}{R}

  • IR3=53600.01389A(13.89mA)I_{R3} = \frac{5}{360} \approx 0.01389 \, \text{A} \, (13.89 \, \text{mA})
  • IR4=53600.01389A(13.89mA)I_{R4} = \frac{5}{360} \approx 0.01389 \, \text{A} \, (13.89 \, \text{mA})
  • IR5=54700.01064A(10.64mA)I_{R5} = \frac{5}{470} \approx 0.01064 \, \text{A} \, (10.64 \, \text{mA})

Check total current: IT=IR3+IR4+IR5I_T = I_{R3} + I_{R4} + I_{R5} IT=13.89+13.89+10.6438.5mAI_T = 13.89 + 13.89 + 10.64 \approx 38.5 \, \text{mA}


5. Calculate the power for each resistor and the total power

The power dissipated by each resistor is calculated using the formula:

P=I2RP = I^2 R

  • PR3=(0.01389)23600.0694W(69.4mW)P_{R3} = (0.01389)^2 \cdot 360 \approx 0.0694 \, \text{W} \, (69.4 \, \text{mW})
  • PR4=(0.01389)23600.0694W(69.4mW)P_{R4} = (0.01389)^2 \cdot 360 \approx 0.0694 \, \text{W} \, (69.4 \, \text{mW})
  • PR5=(0.01064)24700.0529W(52.9mW)P_{R5} = (0.01064)^2 \cdot 470 \approx 0.0529 \, \text{W} \, (52.9 \, \text{mW})

Total power: PT=PR3+PR4+PR5P_T = P_{R3} + P_{R4} + P_{R5} PT=0.0694+0.0694+0.05290.1917W(191.7mW)P_T = 0.0694 + 0.0694 + 0.0529 \approx 0.1917 \, \text{W} \, (191.7 \, \text{mW})


Summary of Results:

  1. RT=130ΩR_T = 130 \, \Omega
  2. IT=38.5mAI_T = 38.5 \, \text{mA}
  3. Currents:
    • IR3=13.89mAI_{R3} = 13.89 \, \text{mA}
    • IR4=13.89mAI_{R4} = 13.89 \, \text{mA}
    • IR5=10.64mAI_{R5} = 10.64 \, \text{mA}
  4. Powers:
    • PR3=69.4mWP_{R3} = 69.4 \, \text{mW}
    • PR4=69.4mWP_{R4} = 69.4 \, \text{mW}
    • PR5=52.9mWP_{R5} = 52.9 \, \text{mW}
    • PT=191.7mWP_T = 191.7 \, \text{mW}

Let me know if you want detailed calculations for any part!


Questions for Further Understanding:

  1. How does connecting points A and D change the circuit's behavior?
  2. What happens if R5R_5 is removed from the circuit?
  3. Can you explain why the total power is the sum of the powers of individual resistors?
  4. How would doubling E1E_1 affect ITI_T and the power dissipation?
  5. What methods can be used to simplify more complex parallel and series circuits?

Tip: Always double-check your total current and resistance when working with parallel circuits to ensure consistency with Ohm’s law!

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Math Problem Analysis

Mathematical Concepts

Ohm's Law
Parallel Circuits
Electric Power Calculation

Formulas

1 / RT = 1 / R1 + 1 / R2 + ... + 1 / Rn
I = V / R
P = I^2 * R

Theorems

Ohm's Law
Parallel Resistance Formula

Suitable Grade Level

Grades 10-12