Electric Circuits

Current Basics

Electric current, charge flow, complete paths, and the conditions required for a circuit

 

Current Basics lesson illustration

 

In the instructor's analogy,
what does the water current represent?

 

 

 

 

Show Me The Physics
YouTube Channel

 

Fill in the Blank Notes

 

D) Conditions for passing current

 

Voltage, Resistance and Current

Fill in the Blank Notes

 

1) complete circuit

Current Basics lesson illustration

 

2) potential difference (voltage) supplied by some source

ex. Battery, generator

 

3) conductor (wires)

 

Current Basics lesson illustration

 

 

I. Important Circuit Terms

 

A) Current (I) - measure of charge flow

 

Current Basics lesson illustration

Click on this link if your school blocks flash CurrentVideoQT.htm

Scientific Advisors: Dr. Saul Dushman; Dr. Roman Smoluchowski; Dr. David Harker

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Production Company: Wolff (Raphael G.) Studios, Inc. Audio/Visual: sound, color
Creative Commons license: Public Domain

Electric_Current.mov

Full Size Current Video

 

 

Current Basics lesson illustration

 

I = q/t 

 

q = charge (C)

t = time (sec)

 

= (C)/(sec) UNIT

OR Amperes

 

 

Ex) If 10. coulombs of charge are transferred through an electric circuit in 5.0 seconds, then the current in the circuit is

 

I = 10. C/5.0 sec

 

 

I = 2.0 Amps

 

 

 

1 Coulomb = 6.25 x 1018 electrons

(A bundle of Electrons)

p. 1 Reference

 

I =  (#e-)(1.6 x 10-19 C)
t

 

 

Ex) A wire carries a current of 2.0 amperes. How many electrons pass a given point in this wire in 1.0 sec?

 

I =  (#e-)(1.6 x 10-19C)
t

 

 

2.0 A =   (#e-)(1.6 x 10-19 C)
1.0 sec

 

Cross Multiply And Divide

 

2.0 A   = (#e-)
(1.6 x 10-19  C)

 

#e- = 1.3 x 1019

 

(2 sig. figs.)

 

AP Physics

Giancoli - p. 515) 8

 

V = IR

 

9.0 V = I[1.6 ohm]

 

I = 5.6 Amps

I = q/t

q  = It

q = 5.6A(60 sec)

= 330 C

divide by  1.6 x 10-19C

 

= 2.1 x 1021 elect.

 

Current Basics lesson illustration

 

 

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. Electric current (I) is best defined as:

2. 12 coulombs of charge pass through a circuit in 4.0 seconds. What is the current?

3. A wire carries 1.6 A for 1.0 s. How many electrons pass a point? (e = 1.6 × 10⁻¹⁹ C)

4. Which is NOT one of the conditions needed for current to flow?

5. A bulb is connected to a fresh battery, but the switch is open. Why is the bulb off?

NYSSLS Regents Practice · Circuits · Electric Current

Charging a Phone

A phone charger delivers a steady current of 2.0 A to a phone battery for 30. minutes.

How much charge flows into the battery?

▶ Want a challenge? Open 6 more Regents-style questions  (harder · mixed formats)

Challenge score: 0 / 6

Substitute values

C1. A slower 1.5-A charger is used to deliver the same 3600 C of charge to the battery. Substitute numerical values into a mathematical representation that can be used to determine the charging time. Then calculate the time.

t = qI = C A = s
Multiple choice

C2. How many electrons pass a point in the charging cable each second?

Support or Refute · Justify

C3. A student makes the following claim.

Claim: Charge is used up inside the phone battery, so the current in the cable wire returning to the charger is less than 2.0 A.

Place a check mark in either the Support or Refute box. Justify your response.

Determine the value

C4. Determine the total number of electrons that pass a point in the charging cable during the full 30.-minute charge.

N = × 1022 electrons
Multiple choice

C5. How does the direction of conventional current compare with the direction electrons actually move in the wire?

Constructed response

C6. A company designs a “super-fast” charger that delivers 6.0 A instead of 2.0 A. Identify one benefit and one drawback of this design change. Support your benefit with a calculation.

Ohm's Law →