Shock Value/Circuit Lab Question Marathon

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Re: Circuit Lab Question Marathon

Post by killer225whale » May 24th, 2018, 3:06 pm

Schrodingerscat wrote:
Your numbers are off by I think a factor of 2. Quick check: 5V across 2000 ohms is 2.5mA and across 1800 is 2.8mA, for a total current of 5.3mA across 514.3 ohms, for a voltage of 2.7 volts. Thus you have a 9-5-2.7=1.3V discrepancy in the 5V load configuration. Also finding the maximum efficiency may be too messy for a test (even using a graphing calculator to maximize expressions), although you could find the maximum power to the load using Thevenin equivalent, which I do not believe gives maximum efficiency necessarily (without analyzing this specific configuration).
Whoops, only checked the math cursorily and saw a R1 = 0.514 * RL...

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Re: Circuit Lab Question Marathon

Post by Tesel » May 24th, 2018, 5:39 pm

killer225whale wrote:
Schrodingerscat wrote:
Your numbers are off by I think a factor of 2. Quick check: 5V across 2000 ohms is 2.5mA and across 1800 is 2.8mA, for a total current of 5.3mA across 514.3 ohms, for a voltage of 2.7 volts. Thus you have a 9-5-2.7=1.3V discrepancy in the 5V load configuration. Also finding the maximum efficiency may be too messy for a test (even using a graphing calculator to maximize expressions), although you could find the maximum power to the load using Thevenin equivalent, which I do not believe gives maximum efficiency necessarily (without analyzing this specific configuration).
Whoops, only checked the math cursorily and saw a R1 = 0.514 * RL...
Yep, so did I... saw a blatantly easy mistake in my work. Definitely should be double the values I gave you, R1 = 1028 ohm and R2 = 3600 ohm. The math actually checks out this time, unless I'm making another stupid mistake.
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Re: Shock Value/Circuit Lab Question Marathon

Post by UTF-8 U+6211 U+662F » May 31st, 2018, 1:43 pm

Restarting.. (with an easy one because I don't know anything yet) what kind of circuit is a current divider?

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Re: Shock Value/Circuit Lab Question Marathon

Post by PM2017 » May 31st, 2018, 3:25 pm

UTF-8 U+6211 U+662F wrote:Restarting.. (with an easy one because I don't know anything yet) what kind of circuit is a current divider?
Current source in parallel with resistance as well as the branch where you want to divide current.
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Re: Shock Value/Circuit Lab Question Marathon

Post by UTF-8 U+6211 U+662F » May 31st, 2018, 4:09 pm

PM2017 wrote:
UTF-8 U+6211 U+662F wrote:Restarting.. (with an easy one because I don't know anything yet) what kind of circuit is a current divider?
Current source in parallel with resistance as well as the branch where you want to divide current.
Yep, your turn.

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Re: Shock Value/Circuit Lab Question Marathon

Post by UTF-8 U+6211 U+662F » June 18th, 2018, 2:22 pm

Restarting this again :P

A battery with EMF 8 V is connected to a resistor with resistance 5 kOhms. A voltage of 7.9 V is measured across its terminals. Find the internal resistance of the battery.

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Re: Shock Value/Circuit Lab Question Marathon

Post by Things2do » June 18th, 2018, 9:53 pm

A internal resistance of 0.1V?
Although I think resistance is in Ohms...
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Re: Shock Value/Circuit Lab Question Marathon

Post by UTF-8 U+6211 U+662F » June 19th, 2018, 10:04 am

Things2do wrote:
A internal resistance of 0.1V?
Although I think resistance is in Ohms...
A battery with internal resistance can be modeled as an ideal voltage source connected in series to a resistor. 0.1 V would be the voltage drop across that resistor. Use Ohm's law to find the current in the overall circuit and use it again to find the internal resistance.

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Re: Shock Value/Circuit Lab Question Marathon

Post by mdv2o5 » July 9th, 2018, 7:40 am

Restarting this since it's been a while:

63.3 ohms (although with that kind of internal resistance, you should probably get a new battery)

Let's do some physics. How many electrons flow through a point on a wire carrying 30 mA in 30 seconds?

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Re: Shock Value/Circuit Lab Question Marathon

Post by UTF-8 U+6211 U+662F » July 15th, 2018, 8:57 am

mdv2o5 wrote:Restarting this since it's been a while:

63.3 ohms (although with that kind of internal resistance, you should probably get a new battery)

Let's do some physics. How many electrons flow through a point on a wire carrying 30 mA in 30 seconds?
30 mA * 1 A/1000 mA * 30 seconds * 6.24E18 electrons/C = 5.6E18 electrons

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