Introduction to Current Electricity

1.  Use your notes to fill in the table below. The first row is completed for you.

Quantity / Unit / Symbol
Current / Ampere (A) / I
Charge
Voltage
Resistance

2.  How many electrons are in 1 Coulomb of electric charge? ______

3.  Conversions: One Ampere of current is a large unit. In the classroom, current is usually measured in milliamperes, or mA. Use the information below to do the following conversions:
1000 mA = 1 A

a.  2A = mA

b.  500 A = mA

c.  0.15 A = mA

d.  0.00004 A = mA

e.  4.7x10-3 A = mA

f.  2400 mA = A

g.  18 mA = A

h.  354000 mA = A

i.  5 mA = A

j.  6.99x106 mA = A

4.  12.48x1018 electrons is how many Coulombs? ______

5.  If 12.48x1018 electrons flow in a wire for 1 minute (60 seconds), what is the current in…

a.  Amperes? ______

b.  Milliamperes? ______

6.  How many electrons will pass through a wire if the current is 10 mA for 30 seconds?

7.  Voltage is a measure of the amount of potential energy supplied per Coulomb of charge transferred. Use the information below to answer the following questions.
(a Joule is a measure of energy)

a.  What is the voltage of a battery if 6 Coulombs of charge have a total energy of
24 Joules?

b.  A 15 volt battery contains 3 Coulombs of charge. How much energy is the battery capable of delivering?

8.  Ohm’s Law ( V = I x R; Voltage = Current x Resistance ) describes the relationship between voltage, current and resistance in an electric system. Find the missing values in the table below:

Voltage / Current / Resistance
120V / 0.1 A
15 A / 0.04 Ω
5000 V / 0.25 A
240 V / 80 Ω
25 mA / 300 Ω

9.  Solve the following problems. Show your work.

a.  An electric magnet is used to lift scrap iron. The electric part of the magnet has a resistance of 62.5 Ω and requires a current of 3.8 A. Find the operating voltage.

b.  Most outlets in your home supply a voltage of 120 V. What is the resistance of a hairdryer that draws 5 A of current from the outlet?