P3 - Electric Circuits

• Current = Charge / Time
• Potential difference (V) is measured in volts (V). It's also called voltage or P.D.
• The current is the rate at which charge flows through an object.
• Charge is measured in coulombs (C)
• The unit of current is amperes (A)
• Resistance is the opposition to the flow of electric charge, it is measured in ohms (Ω)
• Energy transferred = Charge x Potential difference
• Potential difference is a measure of energy transferred in a circuit
• In a series circuit, the current stays the same and the potential difference is shared between components. In a parallel circuit, the current is shared between components and the potential difference on each branch is equal to the voltage of the cell/battery.
• Ohm’s law states that the current through a component is directly proportional to its potential difference across it when all other factors remain constant.
• When two resistors are connected in series, their total resistance is greater than either individual resistance. When they're connected in parallel, their total resistance is less than any one of them.
• If the potential difference across a component increases by a factor of n, then the current will increase by the same factor.
• If the resistance increases, then the current decreases as there are more collisions with electrons.
• Resistance will slow down the current. So a circuit with a high resistance will need a high voltage to move electrons through.
• Voltage = current x resistance
• If the voltage increases, the current also increases.
• If the resistance increases then the current decreases and the voltage increases
• Power = Current x Voltage
• A series circuit has only one pathway for the current to flow around it so all components have the same current flowing through them at any time.
• The power is measured in watts (W)
• A higher current means that more energy is transferred per second so it has a greater power rating.
• An LED gives out light and only conducts current in one direction
• A thermistor is a resistor that changes it's resistance depending on the temperature of the resistor
• A variable resistor allows the resistance to be controlled
• A fixed resistor is a resistor that has a fixed resistance value and cannot be altered.
• An LDR is a light dependent resistor, which is a resistor that changes resistance depending on the light intensity
• A diode is a one-way valve that allows current to flow in one direction only.
• Power = (current)^2 x Resistance