Flashcards
Electric and Magnetic Fields
Cards in this deck (36)
- 1Electric fieldA region of space in which a charged particle experiences a non-contact force
- 2Coulomb's LawGives the force of attraction or repulsion between two point charges in a vacuum
- 3Electric field strengthThe force per unit charge
Given as a vector where the direction is the way a positive charge would move - 4Point chargeAny body that behaves as if all its charge is concentrated at the centre
- 5Radial fieldField strength can be calculated using \(k\frac{Q}{r^2}\)
- 6Uniform fieldField strength is the same at all points within the field
Field strength can be calculated using \(\frac{V}{d}\)
- 7Electric potentialThe energy that a unit charge could hold in its electrostatic store at a given point
Depends on how far the given point is from the charge creating the electric field and the size of that charge - 8Equipotential linesLines that can be drawn on a field to show where potential is equal
- 9Charging a capacitorWhen connected to a power source, one of the parallel plates builds up negative charge (because it can't get over the gap), which causes negative charges on the other side of the gap to be repelled, making the other plate positively charged
A potential difference is created because work is being done to repel the negative charges and make the positive plate positively charged
A capacitor is fully charged when it can repel all new charges that try to join, meaning its potential difference is the same as the battery - 10CapacitorHas a potential difference across it that creates a uniform electric field
Stores electrical energy (which is equal to the work done) by the battery because it builds up charge and has a voltage - W=VIt - 11Discharging a capacitorAn alternative route is created (usually by a switch) meaning that the charges which are attracted to each other over the capacitor gap can move to each other
The time taken is dependent on the capacitance of the capacitor and the resistance of the circuit - 12Capacitor charge curve: \(Q\) against \(t\)
- 13Capacitor charge curve: \(I\) against \(t\)
- 14Capacitor charge curve: \(V\) against \(t\)
- 15Capacitor discharge curve: \(Q\) against \(t\)
- 16Capacitor discharge curve: \(I\) against \(t\)
- 17Capacitor discharge curve: \(V\) against \(t\)
- 18Time constant \(\tau=RC\)The time taken for the charge/current/potential difference of a discharging capacitor to fall to 37% of its fully charged value
- 19Magnetic fieldA region of space in which a moving charge or magnetic material experiences a non-contact force
- 20Right hand ruleStick your thumb up pointing in the direction of conventional current
The direction of the field induced by the current-carrying wire is the same as the path curling your fingers in would take - 21Fleming's left hand ruleThe direction of force on a current-carrying wire placed in an external magnetic field is perpendicular to both the current direction and the magnetic field
- 22SolenoidAn insulated coil of wire with multiple turns
Usually insulated with an iron core
- 23Magnetic flux \((Φ)\)The amount of magnetic field (i.e. the number of field lines) interacting
- 24Magnetic flux linkage \((NΦ)\)The amount of magnetic field multiplied by the number of turns in the coil
\(=NBAsin(\theta)\) - 25\(F=BIlsin(\theta)\)The force on a current-carrying wire in an external magnetic field
- 26\(F=Bqvsin(\theta)\)The force on a single moving charge in an external magnetic field
- 27Magnetic flux densityThe amount of magnetic flux per unit area
- 28Induced EMFAny change in the magnetic environment of a coil of wire will cause an emf to be induced in the coil
Changes in the magnetic environment of a coil could include moving the magnet, moving the coil, changing the strength of the magnet - 29Faraday's LawThe induced emf is directly proportional to the rate of change of flux linkage
- 30Lenz's LawThe polarity of an induced emf is such that it produces a current whose magnetic field opposes the change which produces it
- 31AlternatorGenerates an alternating current by rotating a coil in a magnetic field
- 32Step-up transformersAn alternating current flows through a primary coil which produces a changing magnetic field in the iron core
The iron core carries the changing magnetic field to the secondary coil which experiences a rate of change of flux linkage hence inducing an alternating voltage of the same frequency as the input voltage
The secondary coil has more turns than the primary so the output voltage is higher - 33Step-down transformersAn alternating current flows through a primary coil which produces a changing magnetic field in the iron core
The iron core carries the changing magnetic field to the secondary coil which experiences a rate of change of flux linkage hence inducing an alternating voltage of the same frequency as the input voltage
The primary coil has more turns than the secondary so the input voltage is higher - 34Transformer equation\(\frac{n_s}{n_p}=\frac{V_s}{V_p}=\frac{I_p}{I_s}\)
Applies when it is an ideal transformer - 35Ideal transformerOne that is 100% efficient
Power in = power out - 36Root mean squareShows the effective average value of something that alternates (e.g. an ac supply) so the average doesn't equal zero
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- A level Physics Flashcards on Electric and Magnetic Fields, created by Emma KEMP on 05/03/2020.
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- Emma KEMP
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