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ElectricForces,Fields,andCircuits

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Attachments

ohm'slawexamplesandworksheet.doc

powerworksheet.doc

SeriesParallelCircuits1.doc

Combinationcircuits1.doc

CombinationCircuits2.doc

CombinationCircuits3.doc

circuitsreview.doc

electrostaticsworksheet.doc

a) If your skin has a resistance of 100,000 ohms, and you touch a 9-volt battery, what current will flow through you?

b) What current will flow through you if you touch 120-volt house potential?

c) Soaked in seawater, your resistance is lowered to 100 ohms. Now how much current will flow through you if you touch the 9-volt battery?

d) Soaked in seawater, what current will flow through you if you touch the 120-volt house potential?

Problems:

SMART Notebook

More Power to You

1. What current flows through a 75 W light bulb connected to a 120 V outlet?

2. A small lamp is designed to draw 300 mA of current in a 6.00 V circuit. What is the resistance of the lamp filament?

3. The resistance of an electric lamp filament is 230 . The lamp is switched on when the line voltage is 115 V. What current is in the lamp circuit?

4. A toaster is to be built that uses 1500 W at a current of 10 A

a) Find the resistance it must have

b) What potential difference would be required?

c) Find the current and resistance of a toaster using 1500 W on a 120 V line.

d) The filament to be used to build these toasters has a resistance of 10 per meter of length. Find the lengths necessary for a) and c).

5. A 150 W lamp filament has a resistance of 96 . Find the current.

6. A toaster rated at 1200 W is used 5.00 minutes per day for 30 days. Find the cost at 6.32 per kWh.

7. At 3.6 per MJ, for one dollar, how long can you use a

a) 100 W lamp?

b) 200 W lamp?

c) 1000 W iron?

8. If you used a 500 W hair dryer for 20 minutes a day, 30 days a month, calculate the monthly cost at 2.8 per MJ.

9. Find the cost of operating a motor that uses 20 A at 225 V for 6.00 hours a day, 23 days per month, at $0.0795 per kWh.

10. The electric energy for an apartment costs $50.00 for 30 days. At 6.32 per kWh, find the average current being drawn on the 120 V circuits.

11. What is the resistance of a 100 W light bulb? A 200 W light bulb? A 60 W light bulb?

12. A computer uses a 240 W power supply. How much does it cost to leave this on 24 hours per day for 30 days if the cost of energy is $0.0632 / kWh?

13. An electric heater has a resistance of 29 and operates on 120 V.

a) How much energy is delivered to the heater in half an hour?

b) The heater is being used to heat a room containing 50.0 kg of air. If the specific heat capacity of air is 1.10 kJ/kgoC and 50% of the thermal energy heats the air in the room, what is the change in air temperature?

c) At $0.08/kWh, what does it cost to run the heater 6.0 h per day for 30 days?

SMART Notebook

Series Circuits

1. Two resistors, R1 and R2 are in series with a 12 V battery. R1 = 10 and R2 = 14 .Find I1, I2, V1 and V2.

2. Three resistors are in series with an ammeter and a battery. If R1, R2 and R3 are3 , 2 , and 1 respectively and the ammeter is reading 7.5 A, find I1, VT, V1, V2,and V3.

3. A battery has a terminal voltage of 24 V, and is in series with R1 = 8 , and R2. Ifthe current is 2 A, find R2, V1, V2, and I2.

4. A battery is connected in series with two resistors of 10 and 20 respectively. Ifthe current in the circuit is 2.0 A, find the potential difference across each resistorand the potential difference of the battery.

5. A battery has an EMF of 8.0 V. It is connected in series with three resistors. R1 = R3 = 3.0 , and R2 = 2.0 . Find the current and potential difference for each resistor, as well as RT, and IT.

Parallel Circuits

1. A 6.0 V battery is combined in parallel with two resistors of 50 and 10 respectively. Find It and the current through each resistor.

2. A 40 volt battery is connected in parallel with three resistors: R1 = 50 , R2 = 10 .,and R3 = 20 . Find IT, V1, V2, V3, I1, I2, and I3.

3. Find the resistance of

a) three 15 , resistances in parallel;

b) eight 24 resistances in parallel;

c) and one thousand 47 resistances in parallel.

4. What potential difference must be applied across the parallel combination of three12 resistances to produce a total current of 1.5 A? What is the current in eachbranch?

5. A 4.0 and a 6.0 resistance are connected in parallel across a 6.0 V battery.

a) What is the total current in the circuit?

b) What is the current in each of the two resistances?

SMART Notebook

Combination Circuits

1.

2.

SMART Notebook

Combination Circuits

1.A load connected across a 12 V battery consists of the resistance R1 = 40 in serieswith the parallel combination of R2 = 30 and R3 = 60 . Find all Vs and Rs by completing a table.

2.Resistors R1 , R2, and R3 have resistances of 15 ., 9.0 and 8.0 . respectively. R1and R2 are in series and the combination is in parallel with R3 to form the load acrosstwo 6.0 V batteries in connected in parallel. Find all Vs and Rs by completing a table.

3.A battery of 20 V connected in series with R1 = 2.0 , R2 = 4.0 , and a parallel combination of R3 = 9.0 and R4 = 6.0 .Find all Vs and Rs by completing a table.

Combination Circuits

1.A load connected across a 12 V battery consists of the resistance R1 = 40 in serieswith the parallel combination of R2 = 30 and R3 = 60 . Find all Vs and Rs by completing a table.

2.Resistors R1 , R2, and R3 have resistances of 15 ., 9.0 and 8.0 . respectively. R1and R2 are in series and the combination is in parallel with R3 to form the load acrosstwo 6.0 V batteries in connected in parallel. Find all Vs and Rs by completing a table.

3.A battery of 20 V connected in series with R1 = 2.0 , R2 = 4.0 , and a parallel combination of R3 = 9.0 and R4 = 6.0 .Find all Vs and Rs by completing a table.

SMART Notebook

Physics 122

Combinations Worksheet #3

1. Two resistors, R1 and R2, are connected in parallel. This combination is in serieswith R3, R4, a battery and an ammeter. If R2 = 45 , R3 = 10 , R4 = 20 , VT = 24 V, and the ammeter reads 0.50 A, find

a) the resistance R1;

b) the current through each resistor;

c) the voltage drop across each resistor;

d) the power dissipated in each resistor.

2.Show how one may connect 100 resistances to get a total resistance within 5% of

a)300

b) 50

c) 80

d) 250

e) 14

3. Three resistors of 4.0 , 5.0 and 20 are connected in parallel. Another resistorof 4.0 and a battery of 16 V are placed in series with the parallel group. What isthe current in the 5.0 resistor?

4. Determine the current and voltage drop for each resistor in the circuit below.

5. Determine the current and voltage drop for each resistor in the circuit below.

SMART Notebook

Circuits Review Sheet

Theory

1. What happens to the equivalent resistance of a parallel circuit as you add resistors?

2. What happens to the equivalent resistance of a parallel circuit as you add resistors?

3. What generalization can we make about the total resistance of a parallel circuit?

4. Is the resistance of an ammeter very high or very low? Explain why.

5. Is the resistance of a voltmeter very high or very low? Explain why.

6. How must you connect a voltmeter and an ammeter to a circuit so that it does not catch fire?

Problems

1. 3 resistors are connected in parallel. If R1 is 12, R2 is 60, and RT is 6, then determine R3.

2. The resistors in #1 are connected to a 12 V battery. Draw the circuit diagram, and determine the current through each resistor.

3. Repeat question #2 if the resistors are connected in series instead.

4. Determine the current through and voltage drop across each resistor in the diagrams below.

a)

b)

c)

d)

SMART Notebook

SMART Notebook

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