Electricity Flashcards
(19 cards)
Why is IV graph for a filament lamp curved?
Current increases, increased temp
More movement in atoms
Increased rate of collisions
Resistance increases as shown by shown by V not proportional to I
What is constant in parallel?
Voltage
What is constant in series
Current
What is the resistance in series ?
Sum of all resistors
What is the resistance in parallel?
Smaller than smallest resistor
What is the current in parallel?
Split into a ratio of the resistances
What is potential difference?
Work done moving a unit charge between two points in a circuit
V=W/Q
What is resistance
The difficulty of current to flow through a component
V=IR
What is a diode?
Appliance that only allows current to flow in one direction
What is an LDR?
A light dependent resistor, semiconductor
As light intensity increases, resistance decreases
Describe an experiment for the resistivity of a wire
- Measure diameter of wire with microbe meter and calculate cross sectional area
- Set up circuit with ammeter in series with wire, and voltmeter in parallel. Plus a switch
- Vary the wire length recording voltage and current for each
- Repeat this three times for each length
- Calculate length with averages taken using V=IR
- Plot resistance against length
- gradient gives resistivity / cross sectional are so thus calculate resistivity
What is a superconductor?
A material with zero resistivity below the critical temp
Tends to be around absolute zero
Kirchhoff first law
Current entering a junction = current leaving a junction
Kirchhoff 2nd law
For each loop in a circuit the total p.d across components must equal the emf
What is power?
The rate of energy transfer
What is the purpose of a potential divider?
To split the potential difference between different components
What is the emf?
Electromotive force
Energy transferred by a power supply per unit charge
What are the two uses of superconductors?
Power cables as reduced energy loss
Strong magnetic fields which would not require a constant power source. Could be used in maglev trains where there is no friction
Certain medical applications
What is meant by a potential divider circuit?
Splits the potential difference by the use of resistors in series
