Term 3: Electricity and Waves

Year 9 Summer term core questions

Why are metals such good conductors?

They have delocalised electrons

What is the equation for charge in terms of current?

Q = It

What is one amp?

One coulomb per second

What is voltage?

Energy per unit charge

What is the equation for voltage/potential difference in terms of energy?

V = E/Q

What is one volt?

One joule per coulomb

What is the rule for voltage/potential difference in series circuits?

Voltage is shared across components

What is the rule for voltage/potential difference in parallel branches in a circuit?

The voltage across parallel branches of a circuit is the same

What can we say about components in parallel?

They are at the same voltage

What is Ohm’s law?

Current is directly proportional to voltage

What is the Ohms law formula?

V = IR

In a series circuit, how is the voltage/potential difference of a component related to its resistance?

The voltage is proportional to the resistance

What is an ohmic conductor?

One where current is directly proportional to voltage (obeys Ohm’s law)

How does current affect temperature?

The greater current the greater the temperature

How does temperature affect resistance?

The greater temperature the greater the resistance

How does wire thickness affect resistance?

The thicker the wire the lower the resistance

What is a resistor?

A component that resists the flow of charge

What is the total resistance of resistors in series?

Sum of the resistance of all resistors

Do the same resistors in parallel have greater or less resistance than in series?

Less

When resistances are in parallel, what can we say about their total resistance?

The total resistance is less than the smallest resistance

What does a variable resistor do?

Changes its resistance with manual adjustment

What does a thermistor do?

Lowers its resistance with raised temp

What is an LDR?

Light dependant resistor

What does an LDR do?

Reduces in resistance with brighter light

What does a diode do?

Only allows current to flow in one direction

What is an LED?

Light emitting diode