Physics P2 Unit Opener Picture Puzzler: Key Words Picture Puzzler: Close up Everest, newtonmeter, Earth, remote, gear, yellow The key word is energy. copper wires P2 1.1 Charging up In-text A positive, negative B electron: negative; proton: positive; neutron: no charge Atomic puzzle proton: positive; neutron: neutral; electron: negative; These are the charges on the particles. 1 positive, negative, electrons, repel, attract (5 marks) 2 Electrons are transferred between the balloon and the jumper. The balloon is charged, but the wall is neutral. The charge of the balloon repels like charges from the surface of the wall. (3 marks) Gravitational and electric fields produce forces. You cannot see or feel a gravitational or electric field. They produce non-contact forces. Gravitational fields are produced by masses. Electric fields are produced by charges. Gravitational fields produce forces that only attract. Electric fields produce forces that attract and repel. P2 1.2 Circuits and current In-text A charge flowing per second B ammeter Confusing words charge: the electron has a negative charge; there is a charge to go into a theme park current: current is the amount of charge flowing per second; there can be a strong current in the river cell: component that pushes charge around a circuit; the smallest functional unit in an organism/american term for a mobile phone; a police or prison cell 1 charge, second, electrons, ammeter, amps, A (6 marks) 2a Series circuit with battery of cells, motor, and switch. Students should annotate the switch, and explain how this can be switched on and off to control the circuit. (2 marks) b The electrons move/a current flows. (1 mark) Start with a small series circuit with a switch, lamp, and cell. Show that the light comes on as soon as you press the switch. Make the leads longer, and show that this has no effect. Make a really big circuit, and show that the lamp comes on straight away. Use the rope model to show that the bulb comes on straight away if the charges are already in the wires. It does not matter how long the wire is, the bulb still comes on straight away. If the charges were in the battery, there would be a time delay. P2 1.3 Potential difference
In-text A voltmeter B volt Are bigger batteries better? Plan should include how to measure the size of the batteries, decision on diameter/weight/volume, use of voltmeter to measure the potential, difference across the battery, collect a selection of different batteries, measure the size and potential difference, record results in a table, plot the correct graph type. 1 push, energy, voltmeter, rating, rating (5 marks) 2a The potential difference is bigger because the extra cell supplies more energy. (2 marks) b The buzzer would not work, the cells cancel out. (2 marks) Charges flow when you connect a cell or battery. The charges are already in the wires/component. The battery pushes the charges. The size of the push is related to the potential difference. The charges flowing per second are the current. You measure the current with an ammeter. You measure the potential difference with a voltmeter. P2 1.4 Series and parallel In-text A Two from: in a parallel circuit if one bulb breaks the others stay on; components can be turned on and off independently; parallel circuits have more than one loop or branch. B increases Current issues 0.2 2 = 0.1 A This is because current is shared between components in a series circuit. 1 one, more than one, parallel, series (4 marks) 2 The current increases. (1 mark) 3 QWC question (6 marks). Example answers (three for each type of circuit): Series circuit: current is the same around the whole circuit, ammeter reading stays the same, p.d. is shared between components, voltmeter readings for components will add up to the p.d. of the power supply (cell/battery). Parallel circuit: current is split for each branch, the sum of the ammeter readings in the branches will add up to the ammeter reading from the main branch (by the power supply), p.d. is the same for each branch of the parallel circuit, voltmeter readings will be the same on each branch of the parallel circuit. P2 1.5 Resistance In-text A How easy or difficult it is for the charges to pass through a component in a circuit. B ohms What s the resistance?
1 potential difference, resistance, resistance, electrons, energy, conductors, insulators (7 marks) 2 lamp resistance = motor resistance = = = = 7.5 Ω = 30 Ω (4 marks) Both conductors and insulators have resistance. Conductors have many charges that can move readily. Conductors have low resistance. Insulators do not contain many charges that are free to move. Insulators have high resistance. Most conductors are metals that have electrons that are free to move. Current in an insulator would be smaller than the current through a conductor (for the same potential difference). P2 1.6 Magnets and magnetic fields In-text A north and south B use a compass/iron filings How strong? Type of magnet Distance between paperclip and magnet to get it to float (cm) 1 north, south, repel, attract, compass, magnetic field (6 marks) 2 A compass needle always points in a north south direction. The compass needle lines up in the Earth s magnetic field (which does not change). (2 marks) 3 The game instructions and scoring system should include (6 marks): Clear list of instructions. Using magnets to pick up or guide things. Correct use of north/south poles in the game. Scoring system linked to completion/difficulty. Linking scoring system to magnetic field strength/attraction/repulsion. Correct use of magnetic field strength/attraction/repulsion in scoring system. P2 1.7 Electromagnets In-text A magnetic B type of core, number of turns, current
1 current, magnetic field, coil, current, magnetic field (5 marks) 2 Wind a wire around the nail. Attach the ends of the wires to the battery using the leads and crocodile clips. (2 marks) There is a magnetic field around a wire carrying a current. The field is stronger if there are more loops of wire. This is because the fields add together. A bigger current produces a stronger magnetic field. The magnetic material inside the coil becomes magnetised when you put it in a magnetic field. This increases the strength of the electromagnet. P2 1.8 Using electromagnets In-text A electromagnets B To lift cars/sort metals. Recycle those cans! The letter should explain the basic construction of an electromagnet, and that the electromagnet will attract steel cans but not aluminium. 1 trains, relay, current, spins, motor (5 marks) 2 A simple motor contains a coil of wire and two permanent magnets. A current flows in the coil of wire. The coil becomes an electromagnet. The forces between the coil and the permanent magnets make it spin. (4 marks) Electromagnet is on the two walls. A magnetic material is on the doors. When a current flows in the electromagnet there is a magnetic field around it. The magnetic material on the doors is attracted to it. The doors stay open while a current flows. When the fire alarm sounds, the current to the electromagnet is cut. There is no longer a magnetic field around the electromagnet. The magnetic material on the doors is no longer attracted to it. The doors close.
P2 summary End-of-chapter 1a B (1 mark) b Circuit A: connect a lead from the bulb to the battery. Circuit C: turn one of the cells around. (2 marks) 2a Diagram as in page 133 of student book. (2 marks) b A: attract B: repel (2 marks) c You can turn an electromagnet on and off but you cannot turn a permanent magnet on and off. 3 A current flows in a coil of wire, the coil of wire spins in a magnetic field. (1 mark) 4a Credit suitable parallel circuits with two cells on one branch, with a bulb and a switch on two other branches. (2 marks) b parallel (1 mark) c X, Y, X and Y d Attach an ammeter between the bulbs and the switches. (2 marks) 5a Circuit diagram as described. (2 marks) b The push of the battery/energy transferred in a component. (1 mark) c The potential difference that the lamp is designed to work at. (1 mark) d resistance = = = 30 Ω voltage current 12 V 0.4 A (2 marks) 6a Reading on the ammeter is halved, because there is twice the resistance. (2 marks) b The voltmeter reading is halved, there is less energy transferred to the lamp because the current is less. (2 marks) 7 This is a QWC question. Students should be marked on the use of good English, organisation of information, spelling and grammar, and correct use of specialist scientific terms. The best answers will explain in detail how the rod becomes charged and is able to attract the small pieces of paper (maximum of 6 marks). Examples of correct scientific points: Both the rod and cloth contain atoms. Atoms contain electrons, protons, and neutrons. Electrons are negatively charged. Protons are positively charged. When you rub the rod, electrons move from the cloth to the rod (or vice versa). The rod becomes negatively charged/cloth becomes positively charged (or vice versa, as above). The rod repels the electrons on the top of the pieces of paper. The top of the pieces of paper become positively charged. The paper is attracted to the rod. Answer guide for Maths Challenge
Developing Secure Extending 1 2 marks 3 4 marks 5 6 marks Identifies at least one of the variables. Draws one table but with some or all units missing from the headers. Draws one bar chart but with labels on the axes missing. Identifies most of the variables. Draws at least one table with some units in the headers. Draws at least one bar chart or line graph with correctly labelled axes. States that tungsten has the biggest resistance because the electromagnet is weaker. Identifies all of the variables. Draws all the relevant tables with the correct units in the headers. Draws appropriate line graphs and bar charts with correctly labelled axes, including units. Explains why tungsten has the biggest resistance in terms of current.