Current   Voltage   Power   Resistance   EMF

Electricity lab

Resistance of  a wire 

Ohm's law phet

4.1 Current:

1. Electric charge         Electric  current  is one point property       Conventional current           Kirchhoff's junction  law       Drift speed            Units

4.2 Voltage:

1. Two port electrical components: resistors, light bulbs, wires, switches, diodes, capacitors, inductors           Imprecise and vague - voltage is measure for push

2. Voltage is property of two points        Electrical energy            When a current flow through a element an electrical work is done therefore the element is transforming electric energy into another type of energy.   Voltage is electrical energy gained/lost per unit charge     E = Q * V        Voltage is aka potential difference

3. Electric power         Pelectrical = I * V           Efficiency of a motor           Emechanical =  Eelectrical * efficiency         

4. **If Voltage is path independent then a potential exist. And only then the Voltage is equal to the p.d. (potential difference). In electrostatics Voltage is always equal to the p.d.

4.3 Resistance:

1.          Resistivity is property of the material not the geometry

2. I-V curves for battery,  filament bulb, resistor, diode, thermistor      Definition of resistance        

3. Resistivity of a material can depend on temperature or light:

   • Thermistor has negative temperature coefficient (NTC ): when temperature increases then resistivity decreases

   • Incandescent bulb or metals have  positive ( PTC ):  when temperature increases then resistivity increases  

   • Light dependent resistor (LDR): When light  intensity increases then resistivity decreases   

4.4 Battery:

1. EMF     Terminal potential difference           Internal resistance       

2. Batteries connected in series and in parallel

3. Solar cell

4. **Maximum power delivered by a battery