Systems 3/4 - Electronics 3 - Diagrams

What do these diagrammatic symbols refer to?

What do these diagrammatic symbols refer to?

1. AC power supply

2. Cell

3. Variable Battery

4. Battery

What do these diagrammatic symbols refer to?

1. Capacitor

2. Variable capacitor

3. Polarised capacitor

4. Piezo-electric buzzer

What do these diagrammatic symbols refer to?

1. Diode

2. Zener Diode

3. Light Emitting Diode (LED)

4. Photo Diode

5. Photo Transistor

6. Rectifier (AC > DC)

What do these diagrammatic symbols refer to?

1. Inductor

2. Relay

3. Solenoid

4. Transformer

What do these diagrammatic symbols refer to?

1. Speaker

2. Microphone

3. DC motor

What do these diagrammatic symbols refer to?

1. Resistor

2. Light Dependent Resistor (LDR)

3. Potentiometer

4. Varying Resistor

5. Thermistor

6. Fuse

What do these images refer to?
(They look like this in real life)

1. Diode

2. Light Emitting Diode (LED)

3. Zener Diode

(rare)

1. Which Letters are Anodes/ Cathodes?

2. Which way does conventional current flow for each?

1. Anode: A, C (Anode = ANd = +), Cathode B, D

2. A > B, C > D (Current flows from anode to cathode in all components (draw) other than cells (supply))

1. What is the name for each component?

2. (rare) What is X, Y, Z labeled for each?

3. (tough) Which way does the signal current need to flow to switch on the components?

Bipolar Junction Transistor (BJT), 1 = PNP, 2 = NPN

NPN: X = Emitter, Y = Base, Z = Collector, Flow = Emitter > Base

PNP: X = Collector, Y = Base, Z = Emitter, Flow = Base > Emitter

What do these diagrammatic symbols refer to?

1. Can you identify what this graph refers to?

2. What component uses it directly?

3. (rare) In Australia, what is the peak value for each coloured line and in what units?

4. (rare) What’s the expected frequency?

1. Three phase power

2. AC induction motor

3. 230V in AUS

4. 50hz in AUS

1. Work out which formula you need to calculate the period

2. On a sine wave, what does the period look like?

3. If a transformer reduces the voltage in half, what does the graph look like?

1. f = 1/T is on the sheet (T is time), so T = 1/f

2. Peak to peak is one period, question asks for 2 whole waves.

3. Half the whole height

1. Is this a brushless or brushed DC motor?

2. What is A and B named?

1. Brushless

2. A = stator coils, B = rotor (permanent magnet)

This is an AC induction motor diagram

1. What is A and B named?

2. What makes the green, orange and purple wires different?

1. A = Squirrel cage rotor, B = Stator coils

2. They are separate AC currents out of phase by 120 degrees

(rare)
RMS voltage

1. When would you use this calculation?

2. If you needed to calculate the RMS voltage, what would the equation look like?

1. To convert between AC power peaks and the equivalent constant DC voltage (rectification) (assuming no losses)

2. Vrms = Vpeak/√2

1. What is the voltage at Vs1 and Vs2 assuming no losses?

2. If the measured voltage on the load is 50V, what is the efficiency?

1. 60V

2. 83% approx.

1. (rare) Is there a con to using this simpler rectifier (instead of the full-bridge)?

2. Where would the efficiency losses be?

3. How would the loss appear to a person using the device?

1. Only half of the output coils are used at a time (because of the diode arrangement). Also, half as many diodes = needing higher power diodes

2. The coils, the capacitor, a potential Zener Diode

3. Heat

1. What is this whole component called specifically?

2. Name the 4 labeled parts

Brushed DC motor

1. Stator magnets

2. Rotor coil (rare - armature)

3. Split ring (rare - commutator)

4. Brushes

1. What is this component called specifically and why isn’t it DC?

2. Name the 4 labeled components

Brushed AC motor - the rings don’t have a split in them

1. Stator magnets

2. Rotor coil (rare - armature)

3. Slip rings (rare - commutator)

4. Brushes

What are the names + function for the 3 labeled components?

1. Slip rings - electrical connectors on rotor

2. Rotor coil - when rotates = magnetic field

3. Brushes - electrical connectors to the slip ring and external circuit

(Click on the image to enlarge)

1. What makes this question more difficult than the others?

2. How do you work through it?

1. The lower “started” diagram shows a + and -, so leave off the battery.

2. Draw circles and lines on the top diagram - then copy below

(67% of students got 0 out of 4)

(Click on the image to enlarge)

1. How do you work through it?

2. What trick have they done in the past?

1. Look at each wire between the components and ask yourself “where does it connect”. Usually 2-3 spots. Then, you draw that one, then start the next wire. (1 wire = 1 mark)

2. They have flipped the answer box so you have to draw it flipped

(Click on the image to enlarge)

1. What’s the one tricky bit of this question?

2. How do you complete the circuit?

1. It’s a rectifier and the middle wire is the ground

2. The middle connects to one side of the resistor, the top and bottom to the other end (through the diodes)

Resistance > Current > Voltage > Power

How do you break down the process of calculating total resistance?

1. Circle the parallel resistors (to calculate the total), then imagine it’s one resistor.

2. All that’s left is three resistors in series

(full answer in image)

Resistance > Current > Voltage > Power

Once you have total resistance, which equation gives you the total current draw?

Resistance > Current > Voltage > Power

How do you work out the voltage drop across the circled resistor?

1. Voltage drops in series as a ratio of resistance (voltage division)

2. The voltage division equation is shown in the image

Resistance > Current > Voltage > Power

1. Once you have the the total current and voltage drop, how do you work out the power dissipation in the circled resistor?

2. Would a typical resistor you have used be able to handle this wattage?

1. Refer to the image

2. Most resistors in Systems are 0.5W resistors (sometimes 1W or 2W but exam will specify). It would spectacularly melt and/or catch fire either way

Resistance (2nd harder example)

How do you break down the process of calculating total resistance?

(all other calculations that follow are the same as before, so not repeated)

1. Circle the parallel resistors (to calculate the total), then imagine it’s one resistor.

2. Circle the “combined” resistor with the one other in series, calculate the total.

3. Circle the next two as parallel and calculate that

4. Circle the final “combined” resistor with the last one (in series) and calculate that, which gets you the total.

(I drew another way to visualise the diagram if it helps)

1. Which component is being represented here?

2. (rare) Name the 3 labeled parts

3. Which pin is always connected when it use?

Potentiometer

1. Wiper / Slider

2. Resistive Strip

3. Pins

The middle pin