Electronics

The electronics industry is built around two elements located in the Periodic Table.
These elements are
1. silicon and germanium
2. silicon and chlorine
3. carbon and germanium
4. carbon and silicon
A device which allows current to flow in one direction only is called a
1. diode
2. resistor
3. lamp
4. light dependent resistor
Select the diode from the following four components commonly found in electronic circuits
The photograph shows a typical diode.
Identify the anode and cathode.
1. A = anode, C = cathode
2. A = anode, B = cathode
3. A = cathode, C = anode
4. B = cathode, C = anode
When a diode is forward-biased
1. current flows through it when the anode is connected to the positive end of the power supply.
2. current flows through it when the anode is connected to the negative end of the power supply.
3. current does not flow through the diode under any circumstances.
4. current will flow through it when strong light is shone upon the diode.
A LED is a special type of device that emits light when current passes through it.
Its full name is the light emitting diode. Which one of the following symbols represents the LED?
In the circuit shown, the lamp does not light when the switch is closed. This is because
1. the diode is reverse biased.
2. the voltage across the diode is not strong enough.
3. the diode is probably broken.
4. there is something missing from the circuit.
Which one of the following is a proper use of the diode?
1. To change AC into DC.
2. To light a bulb.
3. To stop current flowing.
4. To measure the current flowing in a circuit.
The picture shows a light emitting diode. Which one of the labelled parts is the anode?
1. A
2. B
3. C
4. D
Which one of the following statements about the LED is not correct?
1. A LED will allow a large current through it.
2. There is a lens at the top of the LED to focus light.
3. The cathode is near the flat side of the LED.
4. The shorter lead entering the LED is the cathode.
Which one of the following is not a use of the LED?
1. To switch on a mobile phone.
2. To indicate whether a device is on or off.
3. In the rear lights of cars.
4. In traffic lights.
Which one of the following is the symbol for the LDR?
Which one of the following statements about the LDR is correct?
1. Current flows through it when bright light is shone on it.
2. Its resistance is very low in the dark.
3. The resistance of an LDR does not change.
4. The LDR is used as a power on/off indicator.
Which one of the following is not a use of the light dependent resistor?
1. Used in heat sensors to detect a change in temperature.
2. Used in switches to turn devices on and off.
3. Used in burger alarms to detect movement of shadows.
4. Used in light meters by photographers.
In the circuit shown, which of the LEDs will light?
1. A and C only.
2. B and D only.
3. All of the LEDs will light.
4. None of the LEDs will light.
Study the circuit shown.
Which of the following statements is correct for this circuit?
1. Both lamp A and lamp B will light.
2. None of the lamps will light.
3. Only lamp A will light.
4. Only lamp B will light.
In the circuit shown which one of the lamps will not light?
1. C
2. A and B
3. B
4. A
Which one of the following devices is most likely to require a resistor in series in order to prevent any large current from damaging the device?
1. Light emitting diode
2. Fuse
3. Lamp
4. Light dependent resistor
In the circuit shown, the bulb does not light. What is the reason for this?
1. The diode is reverse biased.
2. The battery is 'dead'.
3. The fuse has 'blown'.
4. The current passing through the bulb is not large enough.
When electricity is generated in a power station, it consists of alternating current (AC).
In devices such as mobile phones the current is converted to direct current (DC).
Which one are the following devices is used to change AC into DC in the plug/adaptor of the mobile phone?
1. Diode
2. Light dependent resistor
3. Lamp
4. Light emitting diode
In which of the following devices is there an energy conversion from electrical to light energy?
1. Light emitting diode
2. Light dependent resistor
3. Battery
4. Diode
Select the LDR from the following pictures
In the circuit diagram shown, identify A and B
1. A = lamp, B = diode
2. A = lamp, B = light dependent resistor
3. A = resistor, B = light dependent resistor
4. A = switch, B = diode
What happens when light falls upon a light dependent resistor placed in a circuit like that shown?
1. Its resistance decreases.
2. The current going through the LDR decreases.
3. The voltage across the LDR decreases.
4. The LDR begins to glow.
In the circuit diagram shown, identify parts X and Y
1. X = LED, Y = LDR
2. X = LED, Y = lamp
3. X = diode, Y = LDR
4. X = lamp, Y = resistor
A diode is forward biased when
1. the positive terminal of the battery is connected to the anode of the diode.
2. the negative terminal of the battery is connected to the anode of the diode.
3. the positive terminal of the battery is connected to the cathode of the diode.
Mobile phones are charged by using an adapter. In the adapter the mains voltage is reduced from 230 volts down to around 6 volts.
What else does the adapter do in order that the mobile phone can charge properly?
1. It changes alternating current into direct current.
2. It changes direct current into alternating current.
3. It lights a LED to show that it is working.
4. It sends the current in the opposite direction.
Which one of the following is NOT an advantage of using a LED over using a bulb?
1. LEDs can work at high voltages
2. LEDs are cheaper
3. LEDs last longer
4. LEDs use very small current
LEDs are available in a number of different colours. Three of those colours are in the list below. The fourth colour is not yet available for LEDs. Which colour is it?
1. Brown
2. White
3. Red
4. Yellow
The circuit shows a lamp, an LDR and an ammeter in series. What happens when bright light is shone on the LDR?
1. The current in the ammeter increases and the lamp lights more brightly.
2. The current in the ammeter increases and the lamp lights less brightly.
3. The current in the ammeter decreases and the lamp lights more brightly.
4. The current in the ammeter stays the same and the lamp lights more brightly.
Look carefully at circuits A and B.
In which circuit does the red LED light up?
1. B
2. A
3. Neither circuit
4. Both circuits
Look carefully at circuits A and B.
Why is the resistor ‘R’ needed in both circuits?
1. To protect the LEDs from being damaged by a large current.
2. To make sure that only one LED lights in each circuit.
3. To make sure that a current flows around the circuit.
4. To switch on the current in each circuit.
Look carefully at circuits A and B.
Why does the red LED light in circuit B, but not in circuit A?
1. Because the red LED in circuit B is forward biased, and it is reverse biased in circuit A.
2. Because the red LED in circuit B is reverse biased, and forward biased in circuit A.
3. Because the green LED in circuit B is forward biased, and reverse biased in circuit A.
4. Because the voltage in circuit B is sufficient to cause a current to flow, while the voltage in circuit A is not large enough.
The diagram shows a light dependent resistor (LDR) and a graph of the resistance of the LDR against the brightness of light falling on it.
Which one of the following is NOT a use of an LDR?
1. Mobile phone
2. Street lights
3. Light meter
4. Burglar alarm
The diagram shows the apparatus used for measuring the resistance of an LDR at different levels of brightness.
What device is placed at X?
1. Ohmmeter
2. Voltmeter
3. Ammeter
4. Thermometer
The diagram shows the apparatus used for measuring the resistance of an LDR at different levels of brightness.
How is the brightness of the light varied?
1. Moving the source of light closer to or further from the LDR.
2. Using different coloured lights each time the resistance is measured.
3. Connecting a battery to this circuit.
4. By doing the experiment in a dark room.
Light emitting diodes are often used instead of bulbs in electrical circuits.
Why is this?
1. LEDs use less current.
2. LEDs are available in more colours than bulbs.
3. LEDs are smaller than bulbs.
4. It is easier to buy LEDs.
Look carefully at the circuit diagram. Which bulb/s, if any, will light when the switch is closed?
1. A
2. B
3. A and B
4. Neither bulb lights
Look carefully at the circuit diagram. Why does bulb A light and bulb B does not when the switch is closed?
1. The diode at A only is forward biased.
2. The diode at A only is reverse biased.
3. The diode at B only is forward biased.
4. The switch is closed.
Which one of the following materials is used as a semiconductor?
1. Silicon
2. Copper
3. Steel
4. Plastic
A diode must be connected the right way round in a circuit in order to work.
The cathode of the diode can be identified by
1. a coloured band at the cathode
2. a negative sign at the cathode
3. a shorter lead at the cathode
4. the end with the darkest colour
How many electrical connections does a transistor make in a circuit?
1. 3
2. 4
3. 2
4. 1
Which one of the following is not an application of a transistor?
1. Acts as a compass
2. Acts as an amplifier
3. Acts as a switch
4. Controlling current flowing through the circuit
Which current does a diode NOT allow flow?
1. Alternating current
2. Direct current
Which one of the following is NOT TRUE for a light emitting diode?
1. They require a high voltage.
2. They use very little power.
3. They convert electric energy into light energy.
4. They are used as power indicators.
To protect a LED from damage due to a large current
1. a 330 Ω resistor is placed in series with it.
2. an ammeter is placed in series with it.
3. a plastic cover is placed over it.
4. a voltmeter is placed in the circuit.
A LED will work in a circuit no matter what way it is turned.
1. FALSE
2. TRUE
A device whose resistance changes with the amount of light shining on it is known as
1. an LDR
2. a diode
3. a LED
4. an electromagnet
When light falls on a typical light dependent resistor, its resistance will
1. decrease
2. increase
3. stay the same
4. double
Which one of the following is NOT a use of LDRs?
1. TV screens
2. Burglar alarms
3. Lift doors
4. Power indicators

Electronics

Multiple Choice Quiz