Series Circuits

Question 1

When current flows through a resistor, a voltage develops across the resistor. This voltage is called a _____

Answer 1

When current flows through a resistor, a voltage develops across the resistor. This voltage is called a voltage drop.

Question 2

The sum of all the voltage drops in a series circuit equals _______

Answer 2

The sum of all the voltage drops in a series circuit equals the applied voltage.

Question 3

In series circuits, the individual voltage drops depend on the what?

Answer 3

In series circuits, the individual voltage drops depend on the ohmic values of the resistors.

Question 4

The applied voltage is equal to the sum of the voltage drops and is expressed as what?

Answer 4

V_A = Vr1 + Vr2 + Vr3….

or

V_A = I x Rt

Question 5

In which sequence does current flow through these resistors?

Answer 5

R2, R4, R3, R1

Question 6

How do you calculate the voltage drop at a particular resistor?

Answer 6

1st) Determine the current : I_t = V ÷ R_t
2nd) Multiply the resistor by the current (I_t).

R_whatever x I_t = Voltage drop (at that particular resistor)

Question 7

What are the two methods to troubleshooting a circuit?

Answer 7

TRIAL AND ERROR - Using the trial and error method, you replace each part in the circuit until you find the bad part.

LOGICAL PROCEDURE - Using a logical process you do Step 1, then Step 2, and so on, until you know what part is bad.

Question 8

What steps below should be followed when troubleshooting any circuit?

Answer 8

Step 1. Analyze the circuit

1. First, see if the circuit operates correctly. An example is: a television should produce a picture and sound when turned on.
2. If the circuit operates correctly, there is no need to troubleshoot and this would be the last step. If the circuit does NOT operate correctly, then you must go to the next step.

Step 2. Check the setup

1. If the circuit is not operating properly, check to see if you overlooked something simple.
2. For example, if the television does not work, check the: wall plug, atenna, volume control etc.
3. If you checked the setup and the setup is good but the circuit still does not operate properly, go on to Step 3 of the troubleshooting procedure.

Step 3. Calculate and measure circuit values

1. First, calculate to determine the values that should be present in a circuit that is working properly.
2. Make voltage, current, or resistance measurements. Make the measurement that is most useful, and easiest to make.
3. In most cases, voltage measurements are made first. Voltage measurements provide useful information about the circuit and are made without breaking the circuit.
4. If more information is needed, make current or resistance measurements. Remember, a circuit must be broken to make these measurements.
5. Example:
   • Calculate the TV voltages.
   • Measure the TV voltages.
   • Compare the calculated values to the measured values and determine the possible fault.
6. Make as many measurements as needed. As the pieces of the puzzle begin to fall into place, identifying the fault becomes easier.

Step 4. Check the results

1. Compare the calculated to measured values. You should have enough information to identify the fault.

Question 9

What are the three faults are common in a series circuit?

Define them.

Answer 9

Open - when a component provides no path for current flow.

Short - occurs when a component provides no resistance to current flow in a series circuit.

Changed Value - occurs when a component’s ohmic value increases or decreases.

Question 10

What is an indication that a resistor is beginning to open?

Answer 10

Resistance begins to increase

Question 11

How do you determine if the circuit has an open component?

Answer 11

make voltage measurements.

Measure the voltage drop of each component in the circuit.

If you measure a component that has a voltage drop equal to the applied voltage, you have identified the open component.

Question 12

How do you determine if there is a shorted component in a series circuit?

Answer 12

make voltage measurements.

Measure the voltage drop of each component in the circuit.

There will be NO voltage dropped across the shorted component.

Question 13

What is an indication that a resistor is beginning to short?

Answer 13

resistance begins to decrease

Once the component shorts completely, there is no resistance to current flow. This is like replacing the resistor with a piece of wire.

Question 14

How does the Changed Value of a resistor effect a circuit?

Answer 14

If resistance is increased, current flow is decreased

If resistance is decreased, current flow is increased

Question 15

Wha steps should be taken when doing a Voltage check for determining a faulty component?

Answer 15

1. First, calculate the voltage drop that should be present across each component. To find a bad component in a series circuit, measure the voltage drop of each component in the circuit.
2. Compare the calculated values to the measured values. This will identify that a component has changed value.
3. Check current. The circuit’s current will also change due to the component’s change in resistance. Making resistance and current measurements will help you identify which component has increased in resistance.