Energy and Potential Difference in Circuits

Key Issues

Titles

Chapters

• An electric current in an electrolyte is a movement of ions
• calculate simple combinations of resistors (no more than three resistors which may include two equal resistors in parallel)
• calculate the resistance of two equal resistors in parallel
• calculate the total resistance of resistors in series
• Charge = current x time
• Charging by friction
• Components Connected in Parallel
• Components Connected in Series
• Conductors and insulators
• Conductors in Magnetic Fields
• Current as rate of flow of charge
• Current is a flow of charge
• Current-Potential Difference Graphs
• Current-potential difference graphs are used to show how the current through a component varies with the potential difference across it
• Currents Through Components
• Currents Through Diodes
• Currents Through Resistors
• describe and record diagrammatically simple electric circuits
• describe the effects of varying the current on bulb brightness, motor speed and heater output
• Electric Current
• Electric current in electrolytes is a flow of ions
• Electric current in metals is a flow of electrons
• Electric current is the rate of flow of charge
• Electrical Charge
• Electrical Charge Through Resistors
• Energy transferred = current x voltage x time
• Energy Transformed
• Energy transformed, potential difference and charge are related by the equation: energy transformed (joule, J) = potential difference (volt, V) x charge (coulomb, C)
• Equation of Potential Difference
• For components connected in parallel: the potential difference across each component is the same
• For components connected in parallel: the total current through the whole circuit is the sum of the currents through the separate components
• For components connected in series: the total potential difference of the supply is shared between the components
• For components connected in series: the total resistance is the sum of the resistance of each component
• For components connected in series: there is the same current through each component
• If a magnet is moved into a coil of wire, an electrical potential difference is induced across the ends of the coil
• If an electrical conductor 'cuts' through magnetic field lines, an electrical potential difference is induced across the ends of the conductor
• If the direction of motion, or the polarity of the magnet, is reversed, the direction of the induced potential difference and the induced current is reversed
• If the wire is part of a complete circuit, a current is induced in the wire
• Increasing Induced Potential Difference
• measure current and voltage in series and parallel circuits
• Positive and negative electrostatic charges
• Potential Difference
• Potential difference, current and resistance are related by the equation: potential difference (volt, V) = current (ampere, A) × resistance (ohm, O)
• Power = current x voltage
• recall and use the quantitative relationship between current, charge and time
• recall that charge is measured in coulombs
• recall that in a parallel circuit the sum of the currents in the branches is equal to the current entering the parallel section
• recall that in a series circuit the current is the same everywhere
• recall that in a series circuit the sum of the voltages is equal to the voltage across the whole circuit
• recall that voltages across components in parallel are equal
• Resistance of a Component
• Resistance of a Filimament Lamp
• Resistance of a Thermistor
• Resistance of Light-Dependent Resistors
• Reversing the Direction
• SIMPLE ELECTRICAL CIRCUITS
• Structure of a transformer
• The amount of electrical charge that flows is related to current and time by the equation: charge (coulomb, C) = current (ampere, A) x time (second, s)
• The current through a component depends on its resistance. The greater the resistance the smaller the current for a given potential difference across the component
• The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction
• The current through a resistor (at a constant temperature) is directly proportional to the potential difference across the resistor
• The effect of changing resistance on current
• The Generator Effect
• The generator effect also occurs if the magnetic field is stationary and the coil is moved
• The potential difference provided by cells connected in series is the sum of the potential difference of each cell (depending on the direction in which they are connected)
• The resistance of a component can be found by measuring the current through, and potential difference across, the component
• The resistance of a filament lamp increases as the temperature of the filament increases
• The resistance of a light-dependent resistor (LDR) decreases as light intensity increases
• The resistance of a thermistor decreases as the temperature increases (ie knowledge of negative temperature coefficient thermistor only is required)
• The size of the induced potential difference increases when: the speed of the movement increases, the strength of the magnetic field increases, the number of turns on the coil increases, the area of the coil is greater
• understand that an electric current is a flow of electrons and that it is in the opposite direction to that of a conventional current
• understand the role of conductors, insulators and switches in simple series and parallel circuits
• Voltage = current x resistance
• Voltage is energy transferred per unit charge
• When an electrical charge flows through a resistor, electrical energy is transformed into heat energy
• Wires