Flashcards in Electricity Deck (17)

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1

## define current and give a matching equation

### The rate of flow of charge I = Q/t

2

## Define voltage and give a matching equation

### work done per unit charge V=W/Q

3

## Define Electromotive force and provide a matching equation

###
work done by a voltage source per unit charge

emf = E/Q

4

## give two equations for energy in terms of V

###
E= VQ

E=VIt

5

## Give three equations for power

### P = VI = I²R= V²/R

6

## Give an equation for resistivity

### ρ= RA/L

7

## describe an equation to find resistivity

###
1. measure the diameter of the wire, and find the cross sectional area

2. set up s circuit with a voltmeter in parallel to the wire and an ammeter in series. have a ruler on the wire and crocodile clips determining its length

3. measure V and I for different values of L

4. use R=V/I to find resistance

5. plot R against L and the gradient will be ρ/A

8

## state ohm's law.

### in an ohmic conductor current is directly proportional to voltage at a constant temperature

9

## describe superconductors

###
a superconductor has 0 resistance below their critical temperature.

they can be used in strong magnets and power transmission

10

## In an LDR, describe the trend between light intensity and resistance

### resistance decreases as light intensity increases

11

## describe an I-V graph for an ohmic conductor

### a straight line graph, that intersects the origin

12

## describe an I-V graph for a diode

### an exponential graph upwards in the positive quarter that goes through the origin

13

## state Kirchhoff's laws

###
total current into a junction = total current out

total emf around a loop = total potential difference dropped across the components

14

## describe voltage across components of a parallel circuits

### the voltage dropped across components in parallel is the same

15

## describe a potential divider.

### a group of resistors in series across a voltage source, that splits voltage between resistors in direct proportion to their resistance

16

## explain internal resistance

### the resistance of the materials across a battery or cell, across which some voltage is dropped

17