Electrical Energy Storage, Capactor, Battery, Motor

Click For Summary
SUMMARY

The discussion revolves around calculating the height a small electric motor can lift a 2.2-gram mass using a charged capacitor of 0.39 microfarads connected to a 1.5 V battery. The user, Diana, initially attempted to use the energy stored in the capacitor, calculated with the formula U = 1/2CV^2, and then applied the conservation of energy principle with u = mgy. The confusion arose from unit conversion errors, specifically the need to use kilograms instead of grams in the calculations. Ultimately, the correct approach confirmed the validity of the conservation of energy method.

PREREQUISITES
  • Understanding of capacitor charging and energy storage principles
  • Familiarity with the formula U = 1/2CV^2 for energy calculation
  • Knowledge of gravitational potential energy, expressed as u = mgy
  • Basic unit conversion between grams and kilograms
NEXT STEPS
  • Explore advanced capacitor applications in electric motor systems
  • Learn about energy efficiency calculations in electrical circuits
  • Study the principles of gravitational potential energy in physics
  • Investigate common unit conversion errors in physics calculations
USEFUL FOR

Students in physics or engineering, electrical engineers, and anyone interested in energy storage systems and their applications in motors.

yayirunin2car
Messages
12
Reaction score
0
Here is my problem [the last one of a lot that I already got all right and have to turn in by midnight - so you can sense my frustration, lol.]

A .39microF capacitor is charged by a 1.5 V battery. After being charged, the capacitor is connected to a small electric motor.

a) Assuming 100% efficiency, to what height can the motor lift a 2.2 gram mass?

b) What initial voltage must the capacitor have if it is to lift a 2.2 g through a height of 1 cm?

------
What I tried doing was finding the stored energy using U = 1/2CV^2. Once I got that I plugged it into u=mgy, because for some reason I thought my 'y' would give me the height. The answers I got were wrong though, and I've been wracking my brain and reading the book trying to figure it out, but I'm at a loss.

Thanks in advance for any help, :):).
Diana
 
Physics news on Phys.org
In principle, your method is correct (conservation of energy).

Calculator error? Units? Answer key is wrong?
 
Yes! Thank you! I totally forgot that Joules had 'kg' in it and not 'g.' I'm so happy now I can sleep in peace, :).
 

Similar threads

Capacitor Questions Charging and Discharging
  • · Replies 4 ·
Replies
4
Views
4K
Correct energy transformation about circuit with EMF, a resistor and a motor
  • · Replies 11 ·
Replies
11
Views
2K
Electrical and Mechanical Energy as it relates to Capacitors
  • · Replies 12 ·
Replies
12
Views
2K
Electric Potential Energy of Point Charge Systems
  • · Replies 2 ·
Replies
2
Views
1K
Determining Inductance L in an LC Circuit
  • · Replies 5 ·
Replies
5
Views
2K
Calculate Efficiency of Motor Lifting 0.050kg Block at 0.40m/s
  • · Replies 36 ·
2
Replies
36
Views
6K
Why Is Work Positive When Done Against the Electric Field?
  • · Replies 22 ·
Replies
22
Views
4K
Time dependant Potential Energy in ion trap
  • · Replies 1 ·
Replies
1
Views
2K
Minimizing the Energy of Two Conductors Very Far Apart
  • · Replies 23 ·
Replies
23
Views
2K
Electric car and battery problem
  • · Replies 12 ·
Replies
12
Views
2K