3.5 Electricity Flashcards
Define current
Rate of flow of charge
Define potential difference
Work done moving a unit charge between two points in a circuit
Define ohmic
Current is directly proportional to potential difference
What is the represented by the gradient of V/I graph?
Rate of change of V with respect to I
not R or 1/R
Increasing current increases resistance of filament lamp. Why?
- In lamp, electrical energy is converted to heat energy
- Metal ions in the lamp vibrate with increased amplitude
- So there is an increased rate of collision between ions and electrons
- This impedes their movement
- Resistance has increased
What is an LDR?
- A light dependent resistor
- It is a semiconductor sensitive to light
- As light intensity increases, its resistance decreases
Define emf
Chemical energy converted into electrical energy per coulomb of charge passing through cell
2 applications of superconductors
- Power cables (to reduce energy loss)
- Strong magnetic fields (e.g. maglev trains)
What is a superconductor?
Material with resistivity of zero at or below a critical temperature
2 equations for emf
e = I(R+r)
e = V + Ir
3 definitions of internal resistance
- the resistance of the materials within the battery
- hindrance to flow of charge in battery
- loss of pd per unit current
What is a diode?
An appliance that only allows current to flow in one direction
What is the minimum voltage required across a diode in order for it to pass a significant current?
Approximately 0.7V
What is the purpose of a potential divider?
- To provide variable potential difference
- Or to provide a constant specific potential difference
Application of a thermistor
Temperature sensor
