Topic 10 Flashcards
Done
10.1
Describe the structure of an atom
-Mass conc in middle
-Nuc: + proton & neutral neutron
-Negative e^- orbit nuc in energy levels
10.3
State the difference between a series and parallel circuit
-S: 1 complete loop
-P: 2 or more loops connected together
10.5
Define the term voltage
How much I flows
10.5
Define the term potential difference
E transferred per unit charge
10.5
State the unit used to measure potential difference & another unit that means the same thing
-Volts (V)
-Joule per coulomb
10.6
State the equation for energy transferred, charge and voltage. Include units
-E=Q×V
(Energy=Charge×p.d)
-E=J
-Q=C
-p.d=V
10.8
a) Define the term current
b) How does current flow in metals?
a) Rate of flow of charge
b) Flowing electrons
10.8
State 2 ways the current in a metal can be increased
-Increase V
-Decrease R
(Increase no. of e^-?)
10.9
State the equation for charge. Include units
-Q=It
(Charge=Current × time)
-Q=C
-I=A
-t=s
10.10
What happens in a closed circuit when there is potential difference?
There will be current
10.11
Compare the movement of current in a series and parallel circuit
-S: Constant everywhere
-P: Splits between loops (conserved at junctions)
10.11
Compare the movement of potential difference in a series and parallel circuit
-S: Splits between components
-P: Constant on each branch
10.12
Explain the effect of increasing the resistance in a circuit on the current
-e^- collide w/ +ions more -> slow down
-Decreases I
10.12
Compare a fixed and variable resistor
Fixed
-Has constant value
-Therefore provides constant resistance
Variable
-No fixed value (change as I changes)
10.12
What will components in a circuit act as? Why?
-Variable resistors
-R depends on I flowing through them
10.12
Define the term resistance
How difficult it is for I to flow
10.13
State the equation for voltage. Include units
-V=IR
(p.d=current/resistance)
-V=V
-I=A
-R=Ω (ohms)
10.14
Explain whether resistors in series or parallel would have a higher resistance
-Series
-Only 1 path e^- can flow through
-P= e^- have 2 paths
10.15
In a series circuit, the current is 10A and the voltage comes from a mains supply, calculate the resistance
-V=IR
-230=10×R
-R=230/10
-R=23Ω
10.16
Suggest 2 disadvantages of using a series circuit rather than a parallel circuit
-1 component breaks -> whole circuit breaks
-Components can’t be controlled separately
10.17
When devising an experiment with current, what voltage should you not exceed?
15V
10.18
Explain what a diode is and how it works
a) -Component
-Allows I to pass
-In only 1 direc
b) -Has more R in 1 direc than the other
10.19
Describe how an LDR works
(What does LDR stand for?)
-Light-dependent resistor
-Light intensity ↑ -> R ↓ -> ↑ I flows
10.20
Describe how a thermistor works
-R depends on temp
-↑ temp= ↓ R -> ↑ I flows thru
10.21 10.16
Explain how the variation of resistance can be measured for any component e.g. a lamp
Circuit w/…
-Battery
-Ammeter
-Variable resistor
-Tested component
-Voltmeter in parallel to component
(Note: To test fixed R, don’t need variable resistor)
10.16
Devise an experiment to measure the resistance of an
a) LDR
b) Thermistor
a) Circuit w/
-Battery
-LDR
-Voltmeter parallel to LDR
-Ammeter
Vary light intensity & take readings
b) Same thing but w/ varying temps instead
10.22 10.23 10.24
Explain the energy transfer that is caused by resistance
-↑ collisions between e^- & +ions in metal -> ions vibrate ↑
-Electrical E transferred to thermal
-Thermal further ↑ R
-Dissipated to surroundings
(resistance causes heat)
10.25
Describe the effect of heating on resistance
-Gain KE
-Ions vibrate more -> collide more w/ e^-
-Harder for e^- to flow
-R increases
10.25
How can unwanted energy transfers be reduced within a wire?
-Use low resistance wires
-↓ collisions -> ↓ vibrations -> ↓ thermal energy dissipated
10.26
Evaluate the advantages and disadvantages of the heating effect of an electric current
Adv:
-Heat could be useful
Dis:
-E loss
-Risk of fire?
-Could overheat -> damage
10.27
State the equation for energy transferred, voltage, current and time. Include units
E=V×I×t
(Energy=current×p.d×time)
-E=J
-V=V
-I=A
-t=s
10.28
Define the term power. State the units
-r. E transferred per second
-Watts (W)
10.30
Explain how the power transfer in any circuit device is related to the potential difference & current
-As p.d ↑ P ↑
-As I ↑ P↑
(P=IV)
10.29 10.31
a) State 3 equations used to find power. Include units
b) How do you know when to use each
a) -P=E/t
-P=I×V
-P=I²×R
Units
-P=W
-E=J
-t=s
-I=A
-V=V
-R=Ω
b) -P=IV when power SUPPLIED
-P=I²R when power DISSIPATED
10.32
Describe how energy is transferred from batteries to the energy of motors and heating devices
-Batteries store d.c. & release
-Convert chemical-> electrical E
10.32
Describe how energy is transferred from a.c. mains to the energy of motors and heating devices
-Supply a.c.
-Transformers step up/down V from mains to match requirement of devices
10.33 10.34 10.35
Compare direct & alternating voltage
Direct
-p.d (charge movement - same thing) 1 direc
-Produced by batteries & cells (when plugged in, only stays in 1 direc)
Alternating
-p.d CHANGES direc
-Produced by generators
Diagrams
https://www.ecosia.org/images?q=alternating%20and%20direct%20current%20graph&addon=opensearch#id=46845DFD76A753BEF8B469192FE81563822A1368
10.36
State 3 features about mains electricity in the UK
-Alternating current
-Voltage = 230V
-Frequency = 50Hz
10.36
Explain why alternating current is better for domestic use
Transferred over long d efficiently
10.36
What does a frequency of 50Hz mean?
I changes direc 50 times per second
10.37
Describe the function of a neutral wire in plugs
-Provides return route
-For I to flow back
-To power station
10.37
Describe the function of a live wire in plugs
-I flows thru wire
-To required parts of appliance
-Maintains p.d of 230V
10.38 10.39
Describe the function of an earth wire in plugs. Explain why it should be connected to the live wire
-Connects metal part of circuit to metal spike in ground (in case live wire detaches & touches metal)
-p.d of 0V = device functioning well
10.38 10.39
Describe the function of a fuse in plugs
-Has wire that melts if I raises above fuse rating
-Breaks circuit
(Extra: If appliance draws too much current
-Affects R -> affects thermal energy produced -> potential fire)
10.40
State the potential difference of…
a) Earth
b) Live
c) Neutral
a) 0V
b) 230V
c) 0V
10.41
Explain 2 dangers of providing a connection between the live and earth wire (electricity)
Fire
-e^- collide w/ +ions -> vibrate -> transfer electrical energy to thermal -> dissipates heat.
-Too many devices close together = fire
Electric shock
-Insulator around wires tears/breaks -> exposed wires
State 4 factors that affect resistance
-Material
-Length of wire (longer = ↑ R) (Proportional)
-Cross section A (↑ A = ↓ R) (Inversely)
-Temp (↑ temp = ↑ R) (Proportional)
1 Watt is the same as …
1 J/s
10.42
Use an example to describe the relationship between the power ratings of domestic electrical appliances and the energy consumed.
-Domestic appliances w/ ↑ P ratings consume ↑ E (directly ∝)
-Kettle w/ ↑ P rating heats water faster than kettle w/ ↓ P rating
What does LED stand for and how does it work?
-Light emitting diode
-Semiconductor: I flows -> emits light
Reminder to do physical cards too
