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Ranking Task

Rank the total resistance  from smallest to largest 

   
   

 

 

Name this Circuit

St. Mary's Physics YouTube Channel

School blocks YouTube? Use file below.

| ConstructingParallelCircuitsYT.mov |

 

 

 

Ex 6)  Series Circuit

a) Find the 'equivalent resistance'

 

 

RT = R1 + R2

 

 

= 2.0 Ω + 1.0 Ω

 

= 3.0 ohms

 

 

 

 

b) Find the current (IT) going through this circuit

 

VT = ITRT

 

12. Volt = IT(3.0 ohms)

 

IT = 4.0 amps

 

 

c) Find potential drop across R1 & R2

 

V = IR

V1=4.0 amps(2.0 ohms)

= 8.0 Volts

 

 

V2 =4.0 amps(1.0 ohms)

= 4.0 Volts

 

 

 

Ex 7)

a) Find combined resistance (RT)

 

VT = IT RT

 

60. volts = (10 amps)RT

 

 

= 6.0 ohms

 

 

 

b) Find the current in R1

 

V1 = I1R1

 

60. Volts = I120. ohms

 

I1 = 3.0 amps

 

 

c) Find I3

 

V3 = VT = 60. volts

 

Use Ohm's Law

V3 = I3R3

 

60. volts = I330. ohms

 

I3  = 2.0 amps

 

 

 

d) Find R2

 

e) Find value of the second resistor

 

 


 


In a Series Circuit:

(or anytime current in resistors are equal)

V = I R

 

Potential difference (V)
 across a resistor
 is proportional to resistance

 

In parallel, V are always equal

 

 

 

Ex 8)

If the voltage drop across the 3 ohms resistor is 4.0 volts then the voltage drop across the 6.0 ohm resistor is

 

3.0 ohms : 4.0 volts

 

6.0 ohms : x

 

x = 8.0 volts

 

 

 

a) Find the total voltage in this series circuit

 

VT = V1 + V2

 

VT = 8.0 V + 4.0 V

 

= 12 V

 

 

b) Find combined resistance in this circuit

 

RT = 6.0 ohms + 3.0 ohms

 

 

RT = 9.0 ohms

 

 

 

c) Total current in this circuit?

VT = ITRT

 

 12 V = IT(9.0 ohms)

 

I= 1.3 Amps

 

 

 

Ex 9)

a) Compare the current through each resistor

 

 

Same (Series Circuit)

 

IT = I1 = I2 = ... 

 


b) Compare the voltage drops in this circuit?

20. ohm resistor has twice the potential difference (voltage)

 

 

 

c) Current in this circuit?

 

 

VT = ITRT 

60. V =  IT(30. ohms)

 

IT  = 2.0 Amps

 

 

c) Potential difference in 20. ohm resistor?

 

 

V = IR

 

= 2.0 amps(20. ohms)

 

= 40. V

 

 

Ex 10) Find R2

August Sampler

 

V = IR

 

First Find RT

8 V = 1 Amp(RT)

 

R= 8 ohms

 

 

 

Find R2

 

RT = R1 + R2

Since

R= 8 ohms

 

R = 6 ohms

 

 

 

 

 

AP Circuits

EMF - max. voltage of source

- internal resistance causes actual V to be lower

Complex Circuits

Ex) Find the potential difference between  X and Y

Convert parallel R to a single R

1/RT = 1/3 + 1/6

1/RT = 3/6

RT = 2 ohms

Series Circuit 4 ohms,
2 ohms, 6 V source

Need V across 2 ohm R

V  = IR

VT  = ITRT

6 V  = IT6 ohms

 IT = 1 amp

V = 2 V

Ex 2)

Find equivalent R between X and Y

1/RT = 1/3 + 1/6

RT = 2 ohms

 

RT = 3 ohms

Ex 3)

Find total current

(A)  0.8 mA   (B)  1.0 mA 

 (C)  2.0 mA  (D) 3.0 mA (E) 6.0 mA

 

Reduce parallel R to single R

1/RT=1/2000+1/6000

1/RT=3/6000+1/6000

RT = 1500 ohms

 

V = IR

12 V = I[4000 ohms]

 

(A)  0.8 mA   (B)  1.0 mA 

 (C)  2.0 mA  (D) 3.0 mA (E) 6.0 mA

 

 

 

Attaching Meters

 

 

 

 

Enrichment

 

 

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