5: Electric Current Flashcards
Define electronvolt
The energy required by an electron as it moves through a potential difference of 1V. 1 eV = 1.6 x 10^-19J
Define electric potential difference
If we move a + charge from the - end of the battery to the + end, we need work since the charge has a higher potential energy at the + end than the - end. The amount of work done per unit charge is defined as the potential difference between the plates.
Define conductor and give examples of it
Material that allows charge to flow through it e.g. Metal
Define insulator and give examples of it
Material that does NOT allow charge to flow through if e.g. Plastic
Define electric current
Flow of charge; higher potential energy at the positive end than the negative. Current flow from positive to negative Current = charge / time Current is defined as in terms of the force per unit length between parallel current-carrying conductors
Define Ohm’s Law
The resistance is constant over a wide range of applied potential differences and therefore the potential difference is directly proportional to the current Volt = Current x Resistance
Asses and define an ohmic and non-ohmic behavior
Ohmic = Volt and current are proportional to each other; straight line in a graph e.g. Metallic conductor Non-ohmic = Volt and current are NOT proportional to each other; curve in a graph e.g. Filament lamp R = V/I
Derive and apply expressions for electrical power dissipation in resistors
All electrical components use energy, the rate at which they use energy is said to be electrical powers used by the device or component P = IV = I^2R = V^2/R
Define electronmotive force (emf)
The emf of a cell is the amount of chemical energy converted to electrical energy per unit charge. Unit = Volt (V) Emf of a source = the potential difference generated
Define the concept of internal resistance (r)
Every electrical element have internal resistance. As the battery ages, ur chemically degrades and the internal resistance increases. This causes the emf of the battery to decrease. E = IR + Ir
Describe ammeter and the use of it
Used to measure the current flowing through a circuit, must be in a series 1. Always connected in a series with a circuit 2. Has a very low internal resistance, so as not to generate a drop in potential
Describe a voltmeter and the use of it
Used to measure potential difference, must be put in parallel 1. Always connected across the device or in parallel 2. Has a very high internal resistance, so as not to draw a large current from the circuit
How do you calculate for resistors in a series?
R1 + R2 + … = R
How do you calculate for resistors in parallel?
1/R = 1/R1 + 1/R2 + … When the resistance is calculated I n brackets, reverse it to get the R. Since 1/R > R/1
Define electrical sensors
An electrical sensor is a device whose electrical properties change with changing physical conditions
