2023-01-17T21:22:03+03:00[Europe/Moscow] en true <p><strong>Resistance</strong></p>, <p>Materials that offer almost no resistance are called _____, and those materials that offer very high resistance are called _____. Conductive materials that offer amounts of resistance between these two extremes are called <strong>_____</strong>.</p>, <p>The resistance of a resistor is dependent upon certain characteristics of the resistor, including _____, _____, _____, and _____.</p>, <p>Resistance equation</p>, <p><strong>resistivity</strong></p>, <p>SI unit of resistivity</p>, <p>The resistance of a resistor is directly proportional to its _____. This factor scales _____: if a resistor doubles its length, it will _____its resistance.</p>, <p><strong>Conduction pathways</strong></p>, <p>The equation for resistance demonstrates an _____ proportionality between resistance and the cross-sectional area of the resistor: if a resistor’s cross-sectional area is doubled, its resistance will be _____.</p>, <p>Most conductors have greater resistance at _____ temperatures. A few materials do not follow this general rule, including _____.</p>, <p>Why do resistors have a greater resistance at higher temperatures?</p>, <p>Ohm's Law</p>, <p>Electrical resistance results in _____, which reflects a drop in _____.</p>, <p>SI unit of resistance</p>, <p>For a given resistance, the magnitude of the current will be proportional to the ...</p>, <p>For a given magnitude of resistance, the voltage drop across the resistor will be proportional to the ...</p>, <p>As current moves through a set of resistors in a circuit, the voltage _____; the current (or sum of currents for a divided circuit) is _____.</p>, <p>No charge is gained or lost through a resistor; thus, if resistors are connected in series ...</p>, <p>Conductive materials, such as copper wires, act as _____, causing a _____.</p>, <p>Even the very sources of emf, such as batteries, have some small but measurable amount of <strong>_____.</strong></p>, <p><strong>Internal resistance</strong>, <strong><em>r</em><sub>int</sub></strong>.</p>, <p>Actual voltage supplied to a circuit (equation)</p>, <p>If a cell is not actually driving any current, then the internal resistance is _____, and the voltage of the cell is _____. For cases when the current is not zero, the internal resistance is _____, and voltage will be _____.</p>, <p>_____ are the one major exception to the rules of internal resistance.</p>, <p>When a cell is discharging, it supplies _____ which flows from the _____ of the cell around the circuit to the _____.</p>, <p><strong>Secondary batteries</strong></p>, <p>When secondary batteries are being recharged, an external voltage is applied in such a way to drive current _____.</p>, <p>In electrochemical terms, a secondary battery acts as a _____ when it discharges and as an _____ when it recharges.</p>, <p><strong>Power </strong></p>, <p><strong>Power </strong>equation</p>, <p>In electric circuits, energy is supplied by the cell that houses a _____, which when allowed to proceed (by the closing of a switch, for example), generates a _____. These electrons, which have _____, convert that energy into _____ as they move around the circuit, driven by the _____ of the cell.</p>, <p>Resistors convert the kinetic energy of electrons to _____.</p>, <p><strong>Power of a resistor </strong>equation</p>, <p>Resistors can be connected into a circuit in one of two ways: either in <strong>_____ </strong>or in <strong>_____.</strong></p>, <p><strong>Resistors in series</strong></p>, <p><strong>Resistors in parallel</strong></p>, <p>For resistors in series, the voltage drops are _____.</p>, <p>Equation for the voltage drop of resistors in series</p>, <p>The resistances of resistors in series are _____</p>, <p>Equation for the resistance of resistors in series</p>, <p><strong>Equivalent</strong> or <strong>resultant resistance</strong></p>, <p>Equation for the current through resistors in series</p>, <p><em>R</em><sub>s</sub> will _____ as more resistors are added, while <em>R</em><sub>p</sub> will _____ as more resistors are added</p>, <p>Equation for the voltage drop of resistors in parallel</p>, <p>Remember Kirchhoff’s loop rule: if every resistor is in parallel, then the voltage drop across _____ must be equal to the voltage of the source.</p>, <p>Equation for the resistance of resistors in parallel</p>, <p>Equation for the current through resistors in parallel</p>, <p>The current will be largest through the pathways with the _____. In fact, there is an _____ between the portion of the current that travels through a particular pathway and the resistance offered by that pathway.</p>, <p>The configuration of resistors in parallel allows for a greater _____, and the effect of connecting resistors in parallel is a _____ in the equivalent resistance.</p>, <p>If a circuit divides into two branches and one branch has twice the resistance of the other, the one with twice the resistance will have _____ the magnitude of current compared to the other.</p>, <p>When <em>n</em> identical resistors are wired in parallel, the total resistance is given by _____.</p>, <p>When <em>n</em> identical resistors are wired in parallel, the current at each resistor is given by _____.</p>, <p>When approaching circuit problems, the first things you need to find are the _____.</p> flashcards
MCAT Physics and Math 6.2: Resistance

MCAT Physics and Math 6.2: Resistance

  • Resistance

    Resistance is the opposition within any material to the movement and flow of charge.

  • Materials that offer almost no resistance are called _____, and those materials that offer very high resistance are called _____. Conductive materials that offer amounts of resistance between these two extremes are called _____.

    conductors

    insulators

    resistors

  • The resistance of a resistor is dependent upon certain characteristics of the resistor, including _____, _____, _____, and _____.

    resistivity, length, cross-sectional area, and temperature

  • Resistance equation

    ρ is the resistivityL is the length of the resistorA is its cross-sectional area

    ρ is the resistivity

    L is the length of the resistor

    A is its cross-sectional area

  • resistivity

    The number that characterizes the intrinsic resistance to current flow in a material is called the resistivity (ρ).

  • SI unit of resistivity

    ohm–meter (Ω · m)

  • The resistance of a resistor is directly proportional to its _____. This factor scales _____: if a resistor doubles its length, it will _____its resistance.

    length

    linearly

    double

  • Conduction pathways

    The number of pathways through a resistor

  • The equation for resistance demonstrates an _____ proportionality between resistance and the cross-sectional area of the resistor: if a resistor’s cross-sectional area is doubled, its resistance will be _____.

    inverse

    cut in half

  • Most conductors have greater resistance at _____ temperatures. A few materials do not follow this general rule, including _____.

    higher

    glass, pure silicon, and most semiconductors.

  • Why do resistors have a greater resistance at higher temperatures?

    Increased thermal oscillation of the atoms in the conductive material, which produces a greater resistance to electron flow

  • Ohm's Law

    V = IR

    V is the voltage drop

    I is the current

    R is the magnitude of the resistance

  • Electrical resistance results in _____, which reflects a drop in _____.

    an energy loss

    electrical potential

  • SI unit of resistance

    ohms ()

  • For a given resistance, the magnitude of the current will be proportional to the ...

    ... magnitude of the emf (voltage) impressed upon the circuit

  • For a given magnitude of resistance, the voltage drop across the resistor will be proportional to the ...

    ... magnitude of the current.

  • As current moves through a set of resistors in a circuit, the voltage _____; the current (or sum of currents for a divided circuit) is _____.

    drops some amount in each resistor

    constant

  • No charge is gained or lost through a resistor; thus, if resistors are connected in series ...

    ... all of the current must pass through each resistor.

  • Conductive materials, such as copper wires, act as _____, causing a _____.

    weak resistors

    drop in electrical potential (voltage)

  • Even the very sources of emf, such as batteries, have some small but measurable amount of _____.

    internal resistance

  • Internal resistance, rint.

    Internal resistance refers to the opposition to the flow of current offered by the cells and batteries themselves resulting in the generation of heat.

  • Actual voltage supplied to a circuit (equation)

    V = Ecellirint

    V is the voltage provided by the cell

    Ecell is the emf of the cell

    i is the current through the cell

    rint is its internal resistance

  • If a cell is not actually driving any current, then the internal resistance is _____, and the voltage of the cell is _____. For cases when the current is not zero, the internal resistance is _____, and voltage will be _____.

    zero, equal to its emf

    not negligible, less than emf

  • _____ are the one major exception to the rules of internal resistance.

    Superconductors.

    When these elements and compounds are cooled to very low temperatures (usually well below 100 K, but the exact threshold varies by material), the resistivity of the material (ρ) completely dissipates, dropping to zero.

  • When a cell is discharging, it supplies _____ which flows from the _____ of the cell around the circuit to the _____.

    current

    positive, higher potential end

    negative, lower potential end

  • Secondary batteries

    A type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or primary battery, which is supplied fully charged and discarded after use.

  • When secondary batteries are being recharged, an external voltage is applied in such a way to drive current _____.

    toward the positive end of the secondary battery

  • In electrochemical terms, a secondary battery acts as a _____ when it discharges and as an _____ when it recharges.

    galvanic (voltaic) cell

    electrolytic cell

  • Power

    Power is measured as the ratio of work (energy expenditure) to time

  • Power equation

  • In electric circuits, energy is supplied by the cell that houses a _____, which when allowed to proceed (by the closing of a switch, for example), generates a _____. These electrons, which have _____, convert that energy into _____ as they move around the circuit, driven by the _____ of the cell.

    spontaneous oxidation–reduction reaction

    flow of electrons

    electrical potential energy

    kinetic energy

    emf

  • Resistors convert the kinetic energy of electrons to _____.

    some other form, depending on the particular configuration of the resistor (it's usually heat or light on the MCAT)

  • Power of a resistor equation

    I is the current through the resistorV is the voltage drop across the resistorR is the resistance of the resistor

    I is the current through the resistor

    V is the voltage drop across the resistor

    R is the resistance of the resistor

  • Resistors can be connected into a circuit in one of two ways: either in _____ or in _____.

    series

    parallel

  • Resistors in series

    All current must pass sequentially through each resistor connected in a linear arrangement

    All current must pass sequentially through each resistor connected in a linear arrangement

  • Resistors in parallel

    Current will divide to pass through resistors separately.

    Current will divide to pass through resistors separately.

  • For resistors in series, the voltage drops are _____.

    additive

  • Equation for the voltage drop of resistors in series

    Vs = V1 + V2 + V3 + ⋯ + Vn

  • The resistances of resistors in series are _____

    additive

  • Equation for the resistance of resistors in series

    Rs = R1 + R2 + R3 + ⋯ + Rn

  • Equivalent or resultant resistance

    The set of resistors wired in series can be treated as a single resistor with a resistance equal to the sum of the individual resistances, termed the equivalent or resultant resistance.

  • Equation for the current through resistors in series

    I = I1 = I2 = I3 = ⋯ = In

  • Rs will _____ as more resistors are added, while Rp will _____ as more resistors are added

    always increase

    always decrease

  • Equation for the voltage drop of resistors in parallel

    Vp = V1 = V2 = V3 = ⋯ = Vn

  • Remember Kirchhoff’s loop rule: if every resistor is in parallel, then the voltage drop across _____ must be equal to the voltage of the source.

    each pathway alone

  • Equation for the resistance of resistors in parallel

  • Equation for the current through resistors in parallel

    I = I1 + I2 + I3 + ⋯ + In

  • The current will be largest through the pathways with the _____. In fact, there is an _____ between the portion of the current that travels through a particular pathway and the resistance offered by that pathway.

    lowest resistance

    inverse relationship

  • The configuration of resistors in parallel allows for a greater _____, and the effect of connecting resistors in parallel is a _____ in the equivalent resistance.

    total number of conduction paths

    reduction

  • If a circuit divides into two branches and one branch has twice the resistance of the other, the one with twice the resistance will have _____ the magnitude of current compared to the other.

    half

  • When n identical resistors are wired in parallel, the total resistance is given by _____.

  • When n identical resistors are wired in parallel, the current at each resistor is given by _____.

  • When approaching circuit problems, the first things you need to find are the _____.

    total (circuit) values