How do I calculate current, power, and force in a circuit with given variables?

  • Thread starter Thread starter KingJaymz
  • Start date Start date
Click For Summary
SUMMARY

The discussion focuses on calculating current, power, and force in a circuit involving a lamp with an internal resistance of 45 ohms, a magnetic field of 10^-5 Tesla, and a train moving at 300 m/s. The user initially calculated the electromotive force (emf) using the formula "emf = Blv," yielding 3.6 X 10^-2 V. Subsequent calculations for current (8.0 X 10^-4 A), power (2.88 X 10^-5 W), and force (9.6 X 10^-8 N) were derived correctly, but a decimal error in the emf calculation affected the final results. The community confirmed the methods used were appropriate, highlighting the importance of accuracy in initial calculations.

PREREQUISITES
  • Understanding of Ohm's Law (V = IR)
  • Familiarity with electromagnetic principles (emf = Blv)
  • Knowledge of power calculations (P = VI)
  • Basic concepts of force in physics (P = Fv)
NEXT STEPS
  • Review the calculation of electromotive force using "emf = Blv" for accuracy
  • Explore the implications of resistance on current flow in circuits
  • Study the relationship between power, current, and voltage in electrical systems
  • Investigate the effects of velocity on force calculations in electromagnetic contexts
USEFUL FOR

Students in physics or electrical engineering, educators teaching circuit analysis, and anyone involved in practical applications of electromagnetic theory.

KingJaymz
Messages
20
Reaction score
0
Hello, I've done all of the calculations on my homework assignment and have gotten what seem to be the mathematically correct answers, but I'm not sure that they logically make sense. This is the diagram and the problem:
diagram.jpg


You are standing on train tracks in such a way that a circuit is completed. You have a lamp in your hands that has an internal resistance of 45 ohms. The track rails are 1.2 meters apart and the magnetic field is coming out of the page with a magnitude of 10^-5 Tesla. There is a train approaching at a velocity of 300 m/s. Find the current in the circuit, the total power used in the circuit and the force exerted on the train.

So I calculated the voltage with the equation "emf = Blv". Is this correct? For an answer, I got 3.6 X 10^-2 V.

To find the current, I used the proper form of "V = IR" and got an answer of 8.0 X 10^-4 A.

In order to calculate the power, I used "P = VI" and used the Voltage and Current values that I had already calculated.
This yielded 2.88 X 10^-5 W.

Finally, I calculated the force using the proper form of the equation "P = Fv".
This required me to divide 2.88 X 10^-5 by 300, giving me 9.6 X 10^-8 N. I might not be thinking about this correctly, but that seems a bit small. Did I screw up somewhere?

Thank you, in advance.
 
Physics news on Phys.org
Your methods look good to me. I think you did make a decimal point error in calculating the emf, which carries through to the other numbers.
 
Thank you very much, especially for pointing out the error in my math. That's a big help.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 13 ·
Replies
13
Views
1K
  • · Replies 21 ·
Replies
21
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 1 ·
Replies
1
Views
755
  • · Replies 2 ·
Replies
2
Views
669
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
3
Views
2K