Download 16) It`s the Law, per Mr Ohm Ω

Technician Licensing Class
These Power Point presentations are available to individuals who
register with The W5YI Group’s HamInstructor.com program.
The presentations are provided by Master Publishing and The
W5YI Group and include material that is covered by U.S. and
International copyrights. They are intended solely for the use of
Registered Instructors using the Gordon West, WB6NOA,
Technician Class, General Class, and Extra Class study manuals
to teach FCC Amateur Radio Licensing Classes. Registration
through HamInstructor.com constitutes a Licensing Agreement
between The W5YI Group and the registered instructor under
which the instructor agrees not to copy or distribute the Power
Point presentations to unauthorized users.
1
Technician Licensing Class
It’s the Law, per Mr. Ohm!
Valid July 1, 2014
Through
June 30, 2018
2
Amateur Radio Technician Class
Element 2 Course Presentation
 ELEMENT 2 SUB-ELEMENTS (Groupings)
•
•
•
•
•
•
•
•
•
•
About Ham Radio
Call Signs
Control
Mind the Rules
Tech Frequencies
Your First Radio
Going On The Air!
Repeaters
Emergency!
Weak Signal Propagation
3
Amateur Radio Technician Class
Element 2 Course Presentation
 ELEMENT 2 SUB-ELEMENTS (Groupings)
• Talk to Outer Space!
• Your Computer Goes Ham Digital!
• Multi-Mode Radio Excitement
• Run Some Interference Protection
• Electrons – Go With the Flow!
 It’s the Law, per Mr. Ohm!
• Picture This!
• Antennas
• Feed Me with Some Good Coax!
• Safety First!
4
It’s the Law, per Mr. Ohm!
5
It’s the Law, per Mr. Ohm!
• T5A10 Go outside your home or condo and gaze at the power
meter measuring the rate at which electrical energy is being
consumed by all the gadgets inside your new ham shack! Luckily,
your modern ham gear won’t consume much energy so your power
bill won’t go up by more than a few cents per month! That power
meter on the side of your house is called a watt meter, and it is
calculating your household voltage times the amount of amperes of
current flowing to keep your radio station powered up!
• T5A02 Power is energy, and power is measured in watts.
6
It’s the Law, per Mr. Ohm!
• T5C08 Power in watts is equal to volts times current in amps. A
100-watt light bulb, running on 110 VAC house voltage, will draw
about 1 amp. The magic circle for power is: P over E I. Cover the
unknown quantity with your finger, and perform the mathematical
operation represented by the remaining quantities.
7
It’s the Law, per Mr. Ohm!
• T5C09 Power is equal to volts times amps. In this problem,
multiple 13.8 volts by 10 amps, and you end up with 138 watts.
This one you can do in your head. Easy as PIE!
• T5C10 Power is equal to volts times amps. Multiple 12 volts by
2.5 amps, and you end up with 30 watts.
8
It’s the Law, per Mr. Ohm!
• T5C11 This time we are calculating for amps, so it is power (120)
divided by voltage (12). Do the keystrokes: Clear Clear 120  12 =
10. Again, just because they list power second in the question, it
still goes on top at P, and they list voltage first in the question, and
that goes on the bottom as E.
I=PE
I = 120 12
I = 10 Amperes
9
It’s the Law, per Mr. Ohm!
• T5D02 Voltage = current x resistance, which is expressed as: E =
I x R. This simple formula, called Ohm’s Law, states the
relationship between voltage, current and resistance in an electrical
circuit.
10
It’s the Law, per Mr. Ohm!
• T5D10 Since we are looking for E in this question, the voltage
across a resistor, cover E with your finger, and you now have I (0.5
amps) times R (2 ohms). Simply multiple these two values to
obtain your answer of 1 volt. On your calculator, which is
perfectly legal in the exam room, perform the following keystrokes:
Clear Clear 0.5 X 2 = and the answer is 1 volt. Commit the magic
circle of success to your memory now!
E=IxR
E = 0.5 x 2
E= 1 volt
11
It’s the Law, per Mr. Ohm!
• T5D11 The question starts out, “What is the voltage across…” so
put your finger across E and see that the current in this question is 1
amp through a 10 ohm resistor. One multiplied by 10 is… 10 volts.
You can do this one in your head.
E=IxR
E = 1 x 10
E= 10 volts
12
It’s the Law, per Mr. Ohm!
• T5D12 This question is looking for voltage, so we know it’s going
to be a simple multiplication of 2 amperes through a 10-ohm
resistor, with 20 volts as the correct answer.
E=IxR
E = 2 x 10
E= 20 volts
13
It’s the Law, per Mr. Ohm!
• T5D01 For current, put your finger over I, and it is voltage (E)
divided by resistance (R).
I=ER
14
It’s the Law, per Mr. Ohm!
• T5D09 Do the keystrokes: Clear Clear 240  24 = 10. Remember,
to calculate current, it is voltage on top divided by resistance on the
bottom.
I=ER
I = 240  24
I = 10 amperes
15
It’s the Law, per Mr. Ohm!
• T5D08 Be careful on this question – they reversed the order of
resistance and voltage that was in the previous question. In your
magic circle, I = 200  100. Calculator keystrokes: Clear Clear 200
(volts on the top)  100 ohms (on the bottom) = 2 amperes.
I=ER
I = 200  100
I = 2 amperes
16
It’s the Law, per Mr. Ohm!
• T5D07 Here they want to know current, so it is voltage (120
volts) divided by resistance (80 ohms). Here are your calculator
keystrokes: Clear Clear 120  80 = 1.5. Be careful that you don’t
reverse your division – they have an incorrect answer, C, just
waiting for you!
I = E R
I = 120  80
I = 1.5 amperes
17
It’s the Law, per Mr. Ohm!
• T5D03 Put your finger over resistance in the magic circle, and see
that it is voltage divided by current.
R=EI
18
It’s the Law, per Mr. Ohm!
• T5D04 Be careful – they list current first which would go in the
bottom of your magic circle, and voltage at the top. Keystrokes:
Clear Clear 90  3 = 30.
R=EI
R = 90  3
R = 30 ohms
19
It’s the Law, per Mr. Ohm!
• T5D05 In this problem, they list voltage first which is 12, on the
top, divided by 1.5 amps on the bottom. Clear Clear 12  1.5 = 8.
Read each question carefully because they switch around voltage
and current, yet your magic circle always says to put voltage on the
top and current on the bottom when solving for resistance.
R=EI
R = 12  1.5
R = 8 ohms
20
It’s the Law, per Mr. Ohm!
• T5D06 Now remember, Gordo’s rule – on most Technician Class
questions, you divide the larger number by the smaller number, and
presto, you end up with the correct answer. 12 divided by 4 equals
3, correct? R = E (12 volts) ÷ I (4 amps). Ohm’s Law – simple!
R=EI
R = 12  4
R = 3 ohms
21
It’s the Law, per Mr. Ohm!
22
It’s the Law, per Mr. Ohm!
23
Element 2 Technician Class
Question Pool
It’s the Law, per Mr. Ohm!
Valid July 1, 2014
Through
June 30, 2018
24
T5A10
Which term describes the rate at which electrical
energy is used?
A.
B.
C.
D.
Resistance
Current
Power
Voltage
25
T5A02
Electrical power is measured in which of the
following units?
A.
B.
C.
D.
Volts
Watts
Ohms
Amperes
26
T5C08
What is the formula used to calculate
electrical power in a DC circuit?
A. Power (P) equals voltage (E) multiplied by
current (I)
B. Power (P) equals voltage (E) divided by
current (I)
C. Power (P) equals voltage (E) minus current
(I)
D. Power (P) equals voltage (E) plus current (I)
27
T5C09
How much power is being used in a circuit when
the applied voltage is 13.8 volts DC and the
current is 10 amperes?
A.
B.
C.
D.
138 watts
0.7 watts
23.8 watts
3.8 watts
28
T5C10
How much power is being used in a circuit when
the applied voltage is 12 volts DC and the current
is 2.5 amperes?
A.
B.
C.
D.
4.8 watts
30 watts
14.5 watts
0.208 watts
29
T5C11
How many amperes are flowing in a circuit when
the applied voltage is 12 volts DC and the load is
120 watts?
A.
B.
C.
D.
0.1 amperes
10 amperes
12 amperes
132 amperes
30
T5D02
What formula is used to calculate voltage in
a circuit?
A. Voltage (E) equals current (I) multiplied by
resistance (R)
B. Voltage (E) equals current (I) divided by
resistance (R)
C. Voltage (E) equals current (I) added to
resistance (R)
D. Voltage (E) equals current (I) minus
resistance (R)
31
T5D10
What is the voltage across a 2-ohm resistor if a
current of 0.5 amperes flows through it?
A.
B.
C.
D.
1 volt
0.25 volts
2.5 volts
1.5 volts
32
T5D11
What is the voltage across a 10-ohm resistor if a
current of 1 ampere flows through it?
A.
B.
C.
D.
1 volt
10 volts
11 volts
9 volts
33
T5D12
What is the voltage across a 10-ohm resistor if a
current of 2 amperes flows through it?
A.
B.
C.
D.
8 volts
0.2 volts
12 volts
20 volts
34
T5D01
What formula is used to calculate current in a
circuit?
A. Current (I) equals voltage (E) multiplied by
resistance (R)
B. Current (I) equals voltage (E) divided by
resistance (R)
C. Current (I) equals voltage (E) added to
resistance (R)
D. Current (I) equals voltage (E) minus
resistance (R)
35
T5D09
What is the current flowing through a 24-ohm
resistor connected across 240 volts?
A.
B.
C.
D.
24,000 amperes
0.1 amperes
10 amperes
216 amperes
36
T5D08
What is the current flowing through a 100-ohm
resistor connected across 200 volts?
A.
B.
C.
D.
20,000 amperes
0.5 amperes
2 amperes
100 amperes
37
T5D07
What is the current flow in a circuit with an
applied voltage of 120 volts and a resistance of 80
ohms?
A.
B.
C.
D.
9600 amperes
200 amperes
0.667 amperes
1.5 amperes
38
T5D03
What formula is used to calculate resistance in a
circuit?
A. Resistance (R) equals voltage (E) multiplied
by current (I)
B. Resistance (R) equals voltage (E) divided by
current (I)
C. Resistance (R) equals voltage (E) added to
current (I)
D. Resistance (R) equals voltage (E) minus
current (I)
39
T5D04
What is the resistance of a circuit in which a
current of 3 amperes flows through a resistor
connected to 90 volts?
A.
B.
C.
D.
3 ohms
30 ohms
93 ohms
270 ohms
40
T5D05
What is the resistance in a circuit for which the
applied voltage is 12 volts and the current flow is
1.5 amperes?
A.
B.
C.
D.
18 ohms
0.125 ohms
8 ohms
13.5 ohms
41
T5D06
What is the resistance of a circuit that draws 4
amperes from a 12-volt source?
A.
B.
C.
D.
3 ohms
16 ohms
48 ohms
8 ohms
42