Electric circuits

Question 1

Ohmic conductor

and obvious opposites of non-ohmic conductors

Answer 1

Conductor with resistance that is constant for a wide range of :
-voltages
-currents
and obeys ohms law

Question 2

Voltage

and unit analysis

Answer 2

Difference in electric potential energy per unit charge measured across two points
V = J.C-1
V=W/Q

Question 3

Current

Answer 3

Measure of electric charge passing through a conducting material/point per unit time
A = J.C-1
I = Q/t

Question 4

Emf

Answer 4

Electric potential difference between terminals of a battery when NO current is flowing.
OR
Energy per unit charge needed to move an electron from + to - terminal of the battery
V= J.C-1

Question 5

Resistance

Answer 5

obstacle to the flow of charge
- Ration of voltage over current strength
1 ohm = 1 V.A-1

Question 6

Ohm’s law

Answer 6

The potential difference across a conductor is directly proportional to the current in the conductor at constant temperature.

Question 7

Power

Answer 7

The rat eat which work is doen ( P = W/t)
The rate at which electrical energy is transformed /converted into other forms of energy

W = J.s-1

Question 8

Voltage and current in series and parallel circuits

Answer 8

Series: Current =, voltage /
Parallel: Current /. voltage =

Question 9

Note on energy given per electron through the circuit in relation to resistors’ effects

Answer 9

Every Coulomb that goes through the circuit loses the same # energy.

Different resistors limit the amount of coulombs NOT THE ENERGY PER COULOMB (thus resistor affect current not voltage as V = W/Q)

Question 10

Internal resistance

Answer 10

The resistance inside a cell due to the loss of electric potential energy per coulomb as charge leaves/enters the cell

Question 11

4 factors affecting r

Answer 11

1. Size of cell
2. Chemical properties
3. Age
4. Temperature
5. Current of the battery

Question 12

Terminal potential difference (Vload)

Answer 12

Potential difference across the terminals of a battery when there IS A CURRENT flowing in the circuit
Vload = IRext

Question 13

Lost Volts

Answer 13

The difference between the emf and the terminal potential difference
Emf = Vint + Vload
Vint + Vext

Question 14

Short circuit and 2 consequences

Answer 14

A path of very low resistance

What happens?
R tends to zero and I tends towards Imax

Consequences:

• The wire heats up rapidly
• the cell goes flat very quickly

Question 15

Faraday’s Law

Answer 15

The magnitude of the emf induced in a coil is proportional to the rate of change of magnetic flux
Emf = -N Phi/delta t

Question 16

Why is a current induced in a wire coil when it is rotated in a magnetic field.

Answer 16

The coil has a fixed surface area. The number of field lines through the surface changes as the coil rotates so the flux changes over time. The change in flux induces an emf. If the coil is part of closed circuit then the current flows.

Question 17

Rms

Answer 17

Rms value of ac is the DC potential difference or current which dissipates the same amount if energy as ac