P4 Flashcards
What is the unit for charge?
coulombs (C)
charge flow=
current x time
Q= I x t
What’s the equation linking charge flow, potential difference and energy transferred?
Energy transferred = charge flow x potential difference
E = Q x V
current:
the rate of flow of electrical charge
potential difference:
the energy transferred to a component by each coulomb pf charge that passes through it
the greater the ____ of a component, the smaller the ___ for a given potential difference across the component
- resistance
- current
An electric current flows when _______. The moving electrons can ______. This makes it more difficult for the current to flow, and causes ____. The longer the wire, the _______ and so ____
- electrons move through a conductor, such as a metal wire
- collide with the ions in the metal
- resistance
- more collisions
- higher resistance
Describe the relationship between resistance and current
as resistance increases, current increases
Describe and explain the relationship between resistance and temperature
as resistance increases, temperature increases
the ions in the metal filament vibrate more as temperature increases, so they resist the passage of electrons more
in a series circuit (4)
- current is the same through each component
- the total potential difference of the power supply is shared between components
- the total resistance of two components is the sum of of the resistance of each component
- R total = R1 + R2
in a parallel circuit (3)
- the potential difference across each component is the same
- the total current through the whole circuit is the sum of the currents through the separate components
Describe the relation between resistance of an LDR and light intensity
- as light intensity increases, resistance decreases
What are LDRs used in?
turning on streetlights
Describe the relation between resistance of a thermistor and temperature
As temperature increases, resistance decreases
What are thermistor’s used for?
thermostats
equation for potential difference
V = IR
potential difference = current x resistance
resistance of a wire RP: aim
investigate factors such as affecting the resistance of electrical circuits including the length of a wire at constant temperature and combinations of resistors in series and parallel
resistance of a wire RP: variables
IV- length of wire
DV- current and potential differnce to calculate resistamce
CV- thickness and material of wire, temperature
resistance of a wire RP: equation
V= IR
resistance of a wire RP: equipment
battery, variable resistor, wires, voltmeter, ammeter, switch
resistance of a wire RP: method
1. set up circuit with 10cm ___
2. set ___ to 2V
3. close the ___ and record ____ and ____ on the ammeter and voltmeter
4. ____
5. Calculate ___ for each length
6. plot a graph of ____ vs _______
- wire
- power supply
- switch, current, potential difference
- repeat
- resistance
- resistance, length of wire
I-V characteristics RP: aim
investigate I-V characteristics of a variety of circuit elements
I-V characteristics RP: Variables
IV- circuit component
DV- current and potential difference
CV- temperature
I-V characteristics RP: equipment
battery, variable resistor, wires, voltmeter, ammeter, switch, as well as other components to test
I-V characteristics RP: equation
V= IR
I-V characteristics RP: method
1. set up circuit with component set to be tested - ____
2. Set power supply to ____
3. Close switch and record current and potential difference on ___ and ___
4. repeat for a range of ____ by adjusting the ___
5. ____ of the power supply and repeat
6. plot a graph of ____ vs ____
7. repeat for ___ and ___
- fixed resistor
- 2V
- ammeter, voltmeter
- potential differences, variable resistor
- reverse the direction
- potential difference, current
- bulb, diode
ohms law:
the current through a resistor at constant temperature is directly proportional to the potential difference across it
I-V characteristics for a fixed resistor:
directly proportional
I-V characteristics for a filament bulb:
resistance increases as temperature increases (s shaped line)
I-V characteristics for a diode
current only flows one direction, very high resistance in other direction (flat line with sudden peak)
