# P2.4

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What happens when two electrically insulating materials are rubbed together?
Electrons are rubbed off one material and deposited on the other.
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What is charging by friction?
The material that has gained electrons becomes negatively charged and the one that’s lost electrons is left with positive charge.
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What happens with two objects with opposite/same charges?
Opposites attract, same charge objects repel. The bigger the distance, the weaker the force between them
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What are ammeters?
Measure the current through a component + always placed in a series with the component
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What does voltmeter do?
Measure the potential difference across a component – always placed in parallel with the component
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What is the equation relating potential difference, work done and charge?
Potential difference (V) = Work done (energy transferred) (J) ÷ Charge (in coulombs(C)
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What is resistance?
Opposition to the current flow in Ohms (Ὼ). Resistance = Pd(V) ÷ Current(A)
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What are current-potential difference graphs used for?
To show how the current through a component varies with the potential difference across it.
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What is Ohm’s Law?
If the current is directly proportional to the potential difference (pd) across the resistor. Any component that obeys Ohm’s Law is an Ohmic conductor
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What does Ohm’s Law look like on a graph?
If a resistor is kept at a constant temperature, the current-pd shows a straight line passing through the origin.
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What is a series circuit?
Components are connected one after another, so if there’s a break anywhere in the circuit the charge stops flowing.
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What are the key points for the components in a series circuit?
Current is the same in each component. Adding the pds = total pd of supply. Adding the resistances = total resistance of circuit. Bigger the resistance of a component, the bigger its share of the supply pd.
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What is a parallel circuit?
Each component is connected across the circuit-if break in 1 part of circuit, charge can still flow in other parts.
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What are the key points for components in parallel circuits?
Total current = sum of currents through components. Bigger the resistance, smaller the current. Pd same across each component.
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## Other cards in this set

### Card 2

#### Front

What is charging by friction?

#### Back

The material that has gained electrons becomes negatively charged and the one that’s lost electrons is left with positive charge.

### Card 3

#### Front

What happens with two objects with opposite/same charges?

### Card 4

#### Front

What are ammeters?

### Card 5

#### Front

What does voltmeter do?

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