# Help with building Very simple Circuits--Freshman engineering lab.

Discussion in 'Homework Help' started by gabriella schweska, Sep 18, 2015.

1. ### gabriella schweska Thread Starter New Member

Sep 18, 2015
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Hello all,
I have a homework assignment based on one of my Circuit labs that I'm having trouble with, normally I would go to a tutor on campus but the girl that typically helps with circuits is out of town this weekend. We are building simple circuits without a breadboard, using LEDs and a small 1.5 V battery power source that uses four AAs. The Lab was intended as an opportunity for us all to individually build a few simple circuits, but pretty much all of our batteries ended up being corroded so my instructor decided to let one member from each team build the circuits while everyone else watched. I genuinely thought I understood what was going on but when I sat down to do the homework I didn't. I was hoping someone could explain to me how to build the following circuits from the diagrams I attached so I can answer my homework problems. Even pointing me in the direction of existing tutorials would be a huge help.
*I have emailed my professor but I don't expect him to email me back over the weekend.

2. ### Alec_t AAC Fanatic!

Sep 17, 2013
5,976
1,136
Welcome to AAC!
1) Do you understand what the symbols in those circuits represent?
2) Are the four AA cells connected in series or in parallel to form a battery?
3) Is a battery or a single cell represented in those circuits?
4) Have you learnt Ohm's Law?
5) If you are not using a breadboard, how will you connect components to each other?
6) Do you have a plentiful supply of LEDs?
7) What colour are the LEDs?

3. ### WBahn Moderator

Mar 31, 2012
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What are you supposed to do once you have built each of the circuits? Just observe and comment on which, if either, of the LEDs lights up?

Are you not using any resistors at all in these circuits? If not, hopefully the answer to Alec_t's question #6 is, "Yes."

4. ### shteii01 AAC Fanatic!

Feb 19, 2010
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How to build them.

Take battery. One end of battery will have a plus printed on the label. The other end will have a minus printed on the label.

Take led. LED has two "legs". One leg is longer than the other. The longer leg is plus, just like battery. The shorter leg is minus, just like the battery.

Now let us assemble Circuit A.
You have a battery with a plus on one end, minus on another end. You have two led, LED 1, LED 2. Connect the plus leg of LED 1 to plus on the battery, connect the minus of leg of LED 1 to minus on the battery. Now do the same for LED 2.

5. ### ISB123 Well-Known Member

May 21, 2014
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OP:
Are you paying the school or lessons?

6. ### shteii01 AAC Fanatic!

Feb 19, 2010
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I know that, I already have BSEE.
But new people will have to learn how to add batteries to get higher voltages. Remember, they were supposed to have four AA batteries.

7. ### ISB123 Well-Known Member

May 21, 2014
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Or they could just use 2 batteries on a particular circuit and it would work just fine .

8. ### #12 Expert

Nov 30, 2010
16,704
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Please be clear. Does the "power source" provide 1.5 volts or some other voltage?

Apr 30, 2011
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Last edited: Sep 19, 2015
10. ### GopherT AAC Fanatic!

Nov 23, 2012
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I am guessing the lab uses LEDs that have a built in resistor to limit current to prevent them from glowing orange /amber and then not working after about 15 seconds.

Assuming your 4 battery x 1.5 V = 6 volt power pack measures something near 6 volts, then make note of which pins on the LED are anode and cathode.

Then make note of each circuit drawing. Remember that a regular diode and an Light-emitting diode (LED) only let current flow from anode to cathode. If the LED is installed cathode as more positive, no current will flow.

Now, start playing around with that stuff.

Apr 30, 2011
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That's possible. A resistor/LED unit designed for 12V will still work fairly well on 6V. I think I've even seen battery holders with a built-in limiting resistor for student use but since the schematics don't show that, I made a recommendation that will work explicitly as shown.

GopherT likes this.