Electricity Flashcards

Question

Electromotive force (ε)/emf

Answer 1

Kind of has nothing to do w/ force? Defined as the ratio of energy change to charge (so, same def) Units: Jc^(-1) or volts Whatever the battery supplies w/ closed current If it's a series circuit (one continuous loop), voltage is shared (every load shares what the battery provides)

Answer 2

Obstruction of electron flow in battery: the resistance of a cell (ex. battery) When current introduced, conversion Terminal voltage is what is shared Also a type of resistance, but specifically for the battery Causes the conversion of electrical energy to thermal energy inside a battery, leading to shortage in battery output (lower current?) Therefore, the pd when there's current in a circuit (terminal voltage) is less than the output of the battery w/o current (emf) The voltage lost due to internal resistance is called voltage drop/lost voltage (voltage due to internal resistance of cell) Lost volts = Ir So, if battery is not connected in a circuit (no current flows), emf = terminal vo ε = Vterm + Vlost ε = IR + Ir ε = I(R + r) *See equations and apply y = mx + b

Answer 3

ε = change in E/q divide both numerator and denominator by t.... ε = total power/total current total power delivered by battery = εI *Alternative def is ratio of power and current

Answer 4

States that at every junction in a circuit, current in = current out (garbage in = garbage out) sum in = sum out sum = 0 (charge conservation law) If in = out, if you move one to other side, 0 Applies to every circuit

Answer 5

Has all components (resistors) connected in a continuous chain At any point, Kirchoff's 1st Law is true (current same everywhere) But Pd is shared among the different resistors/components Check ans by summing to see if same as voltage supplied by battery Total resistance = R1 + R2 + R3 +... Current same everywhere

Answer 6

Has branches (more than one route for current flow) Pd (voltage) stays the same b/c each has equal connection to battery Current shared Total current is sum Pd same 1/RT = 1/R1 + 1/R2 + 1/R3 +... More resistance = less current No one resistor blocking another b/c not in same line See diagram... Sum first if in series (parallel first if like component in series) and then treat as parallel No dots = in series (circles mean in parallel w/ whatever) B/c parallel, current different in branches, so A measures for whatever's next to...

Answer 7

Once you complete a circuit, battery supplies the energy that pushes the electrons After some time, energy depletes Discharging is the process by which a cell delivers charges to an external circuit The amt of charge a cell can deliver to ab external circuit is known as its capacity The greater the current in the external circuit, the faster the discharge During the discharge, the terminal pd loses its value quickly initially, stabilizes consistently for most of its lifetime, and then decreases rapidly to zero, as the discharge completes *See graph... *Battery we see is just a combo of different cells *Remember charging...

Answer 8

Two types: primary and secondary

Answer 9

Everyday batteries that we know Non-rechargeable In other words, the chemical reactions that produce the pd use up the chemicals Can be used in flashlights, remotes, toys, clocks, watches, etc. ex. alkaline, lithium, zinc oxide batteries gallium?

Answer 10

Rechargeable Done by passing current through the current in direction opposite that of electron flow (regenerates the chemical reactions) During discharging process, current goes in one direction (when recharge, other direction) Used in mobile phones, cars, laptops, tablets, ?PS, SLI (starting on [switching on], lighting [ex. headlights?], ignition [engine]) ex. lead acid batteries (for cars), lithium batteries, nickel ion batteries, etc.

Answer 11

A circuit arranged in a way that two or more resistors divide the supplied pd To use pot formula, have to reduce circuit to series Recall, I = V/R Therefore, is total resistance = R1 + R2, then T = V/(R1 + R2) The pd across R2 = Vout Since V = IR Therefore, Vout = Vin/(R1 + R2) x R2 NOTE: R2 symbolizes the resistor whose voltage (Vout) is being calculated

Answer 12

Used as sensors Two types of sensors: LDR (light-dependent resistor) and thermistor

Answer 13

A variable resistor Special type of resistor where resistance depends on the amt of light shining on it An increase in light results in a decrease in the resistance (voltage) and vice versa ex. sunlight-dependent bulb (uses electronic switch) Resistance can go all the way down to 0, so v will be 0 as well (switch won't turn on [opposite true at night?]) *see circuit

Answer 14

Used in fire alarms Detects presence of fire Variable resistor When it gets hot, its resistance decreases, resulting in decreased voltage (therefore, the voltage of the resistor attached to the alarm switch decreases, turning on the alarm) In series, so have to sum up to the battery's (so, if voltage of one decreases, other increases) *see circuit, note symbol

Answer 15

States that in any closed loop, total emf (cells) = total voltage (pds of all resistors) or total v = 0 NOTE: V = IR

Answer 16

emf is positive if loop is from negative to positive of cell (and negative if opposite) V is positive in loop foes along current direction (negative if opposite)

Answer 17

1. Draw lines to show loop direction (clockwise/counter—doesn't matter as long as you follow the rules) 2. Draw arrows across each cell to show current direction (*conventional?) 3. Name your currents (if junctions [parallel situation] are involved) 4. Apply 1st and 2nd Laws

Answer 18

A region where a magnet/charge/CCC (current-carrying conductor [depending on strength of curr) feels a force Magnets feel force when they enter a magnetic field If they can make a circuit w/ high-capacity batter or to AC (mains) of a , if a heavy object contains a lot of iron, can use In every field, you have a force Current produces electric field (also charge b/c no current w/o charge) Mass produces gravitational field Only iron and other things that contain iron (atoms that align themselves) White will point north Only true test is repulsion (means both have fields): a magnet can attract something that's not a magnet CCW = current-carrying wire W/ the presence of current, a conductor will be able to behave like a magnet Magnets are attracted to southernmost pole of other magnets red end points to geographic north of earth (magnetic south) like w/ iron shavings b/c attracted, compasses same way line red called north seeker

Answer 19

Magnetic fields are represented using field lines, known as flux Magnetic field lines are real (not imaginary like electric field lines)

Answer 20

See... Field strength decreases, so spacing getting bigger A compass aligns itself to direction of magnetic field (pointing south)

Answer 21

See... *Distance also increases An electric current produces a magnetic field NOTE: 1. Field lines around a CCC always circular 2. Direction of magnetic field can be predicted using the right-hand grip rule (if thumb is direction of current, direction of field is natural fingers circle pencil)

Answer 22

See... A solenoid is when you wrap a wire around a conductor (whole system known as a solenoid [more you ) Same as that of a bar magnet NOTE: 1. Poles of a solenoid (can't tell in practice) can be predicted using the right-hand grip rule, but in a *different way* (direction the fingers curl is current direction and direction of thumb is that of the magnetic field)

Answer 23

When a CCC is placed in a magnetic field, it feels a force This force is perpendicular to both the current's direction and the magnetic field's direction *have to be able to sketch) This force (F) is directly proportional to: the magnitude of current (I), the strength of the field (B), the length of the CCC (L), and the sine of the angle between the field and the current F = BILsin theta (if angle not involved, just F = BIL B = F/ILsin theta Unit for B: NA^(-1)m^(-1) or Tesla see formula, use 90 degrees? NOTE: 1. Force is max when current and field lines are perpendicular 2. Force goes down if the theta between current and field lines decreases 3. Force is 0 if both CCC and field lines are parallel The direction of the force of CCC is determined using the following: Flemming's left hand rule (force is thumb, current is middle, and field is first/fore/index [?]) and the right hand palm rule *Rsr...