electricity

• Electric potential is the work needed to move a unit positive charge from infinity to a point in an electric field
• Potential difference is the work done to move a unit positive charge between two separate points
• A bulb will glow or a magnetic needle will deflect if the liquid in the beaker is a good conductor of electricity
• Greater deflection of the needle or brighter light indicates better conductivity of the liquid
• Conducting liquids are also known as electrolytes
• Electric current passing through a conducting liquid causes chemical reactions known as electrolysis
• Ohm's Law states that the current flowing through a conductor is directly proportional to the potential difference across the conductor
• V = IR (R = resistance)
• Ohmic resistors follow Ohm's Law at constant temperature, examples include metallic conductors, copper sulphate solution with copper electrodes, and dilute sulphuric acid
• Non-ohmic resistors do not follow Ohm's Law, examples include LED, solar cell, junction diode, transistor, and bulb filament
• Potential difference (measured in Voltage) causes current (measured in Ampere)
• In conductors, current is the flow of electrons. Electrons flow from the negative terminal of a battery to the positive terminal
• When a battery is not connected to a circuit, the potential difference across its terminals equals the EMF of the battery (EMF = Electro Motive Force)
• Resistance in series connection: Rs = R1 + R2 + R3 + ... + Rn
• Resistance in parallel connection: 1/Rp = 1/R1 + 1/R2 + 1/R3 + ... + 1/Rn
• Joule's heating law states that heat produced in a resistor is directly proportional to the square of the current, resistance of the resistor, and time for which the current flows
• Electric energy = VIt
• Electric power is the rate of consumption of energy or the rate of doing work, measured in watts (W)
• 1 kWh is the commercial unit of electric energy, where 1 kWh = 3.6 × 10^6 J
• 1 W = 1V × 1A