Currents Grade 9

What is voltage?

The difference in electrical potential energy between two points

What is resistance?

Opposition to flow

What is current?

The rate at which electrons flow in a circuit

What is Ohm's Law?

V\=IR (voltage \= current x resistance)

How do you calculate percent efficiency?

Energy out/Energy in x 100

How do you calculate cost to operate?

Cost x time (hours) x usage (in KW)

How do you convert watts to kilowatts?

divide by 1000

How do you use a voltmeter?

A voltmeter needs to be connected parallel to either side of a load because voltage is relative to two points, and there is always a drop in voltage across a load or power source.

How is an ammeter connected in a circuit?

An ammeter needs to be connected in series. The negative side of the ammeter needs to be connected to the negative part of the battery.

Parallel circuit

A circuit that contains more than one path for current flow.

Series circuit

An electric circuit with only one path through which charge can flow

What will happen to resistance if you lengthen a chord?

Resistance will INCREASE because there will be more length for the electrons to flow through

What will happen if you increase the temperature of a chord? (ie. make it warmer)

Resistance will go up because electrons will vibrate and collide with one another.

What will occur with resistance if you increase the diameter of a chord?

Increasing the diameter will REDUCE resistance because there will be more space for electrons to travel freely

What is a better conductor for lower resistance: copper or metal?

Metal

Alternating Current (AC)

An electric current that changes direction at regular intervals

Direct Current (DC)

Electric current that flows in only one direction

What is required for electricity to flow?

A closed circuit

If one bulb burns out in a series circuit, what happens to the other bulbs?

They burn out because there is only one path for electron flow.

If one bulb burns out in a parallel circuit, what happens to the other bulbs?

They continue working because there are multiple paths for electron flow

How is wind energy generated?

Spinning turbines in windmills harness the wind and convert it into energy

Cons of wind energy?

* Unreliable (reliant on wind and the weather)
* Can be harmful to wildlife (e.g. birds)
* Loud noises

How is solar energy generated?

Solar panels absorb energy from the Sun to generate electricity.

What are cons of solar energy?

* Expensive up front
* Large area needed
* Weather dependent
* Daytime only