May'15 Flashcards
Describe the structure of a transformer.
Consists of two separate coils of wire wound on the same iron core
What is the equation used when dealing with transformers?
Vs/Vp= Ns/Np
which is secondary voltage/primary voltage = Number of secondary turns/ number of primary turns
What are the equations for efficiency?
Effieciency= output power or energy/ input power or energy x100%
What can affect the size of an induced voltage when a wire is moved within a magnetic field?
Move the wire faster between the poles
Use a stronger magnet
Use more conductor
How are electrons arranged in a conductor?
They contain electrons which are free to move throughout the structure
How are electrons arranged in a insulator?
The electrons are tightly bound and cannot move.
Describe a series circuit.
When components are connected in line, we say they are connected in series.
What is the unit of current?
Amperes (A)
How do you measure current?
Make a gap in the circuit and connect an ammeter. The reading on the ammeter is the current.
Describe a parallel circuit.
When components are connected so that there is more than one path for the current, we say they are connected in parallel.
What is meant by voltage in an electrical circuit?
It is the electrical energy supplied by the battery to make the electrons move around the circuit.
How do you measure voltage?
Use two extra wires to connect to a voltmeter in parallel with the component.
How is resistance in an electrical circuit measured?
An ohmeter is connected directly across the component which must be disconnected from the circuit.
What is the unit for resistance?
Ohms
What is the equation for Ohm’s Law?
Resistance= voltage/ current which is R= V/ I
What is the equation involving current, charge and time?
current= charge/ time which is: I= Q/t
What is alternating current?
A.C goes up and down and is produced from the main supply.
What is direct current?
D.C ——————— and is produced from a battery.
What is the unit of energy?
Joules, J.
What is the unit of power?
Watt, W
What is the equation involving energy, power and time?
energy= power x time which is: E= Pt
What are the three parts of an electronic system in order?
The input, the process, the output.
What type of device are a thermistor, LDR and switch?
Input
What happens to the resistance of a thermistor when the temperature changes?
High temperature= Low resistance
Low temperature= High resistance
What happens to the resistance of an LDR when the light levels change?
Bright light= Low resistance
Dark light= High resistance
What is an appropriate input device for a loudspeaker and heating system?
Microphone and Thermistor
What is an appropriate input device for an automatic lamp and a lighting circuit?
LDR and Switch
What is the energy change in an output device?
Electrical energy——-> another form of energy.
What type of devices are a loudspeaker, buzzer, lamp, LED and electric motor?
Output
What is an appropriate output device for a warning light, a fan and smoke alarm?
LED, Motor and Buzzer
What does the NOT gate look like?
Continuous line input and output——-
triangle with circle at the end
What does the AND gate look like?
2 lines at start (input A and B) and one line at the end (output)
half circle
What does the OR gate look like?
2 lines at start (input A and B) and one line at the end (output)
triple curved shape
What does the truth table for a NOT gate look like?
Input | Output
0 | 1
1 | 0
What does the truth table for an AND gate look like?
Input A and B | Output 0 0 0 1 0 0 0 1 0 1 1 1
What does the truth table for an OR gate look like?
Input A and B | Output
0 0 0
1 0 1
0 1 1
1 1 1
What is meant by specific heat capacity?
The amount of energy need to raise 1kg of a solid by 1’C.
Measured in J-1Kg’C-1
What is the equation for specific heat capacity?
Energy= specific heat capacity x mass x change is temperature
which is: Eh= cm (Delta)T
What is the equation for work done?
Work done= force x displacement
which is: Ew= Fs
What is the equation for kinetic energy?
Kinetic energy= 1/2 x mass x velocity^2
which is: Ek= 1/2 mv^2
