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30 Cards in this Set
- Front
- Back
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What happens when certain insulating materials rub together?
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They become charged
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When objects become charged, electrons are transferred. What happens to the insulating materials that become positively or negatively charged?
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When rubbed, Positively charged lose electrons and negatively charged gain electrons
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What do like and unlike charges do?
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Like charges repel, unlike charges attract
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What is the process charging by friction?
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A material that loses electrons is left with a positive charge. An insulating metial that gains electrons becomes negatively charged as electrons have a negative charge.
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The bigger the distance between the objects,
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the weaker the force between the.
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What moves to produce positive and negative charges on objects?
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ELECTRONS. ONLY EVER ELECTRONS
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What is an electric current?
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A flow of charge due to an electron being forced to move. measured in amperes.
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To calculate the electric current in a circuit when charge flows, which calculation is used?
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I (current in Amperes) = Q (charge in coulombs) / t (time in seconds)
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What does a battery consist of?
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Two or more cells connected together.
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What is the rate of flow of charge?
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The size of an electric current
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What is the Potential difference equation
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energy transferred (joules) / charge (coulombs)
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What is the equation for resistance (ohms)
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Potential difference (volts) / current (amperes)
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What is Ohm's law?
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The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.
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What does reversing the current through a component do?
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Reverses the potential difference across it.
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That is the opposition to current low?
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Resistance, measured in Ohms (omega sign)
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What is an ohmic conductor?
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Any compnent that obeys ohm's law
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What are Current-potential difference graphs used for?
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To show how the current through a component caries with the potential difference across it.
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Current is not directly proportional to the what?
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Potential difference. Shown by the curve on a current-potential difference graph for a filament bulb.
Reversing the p.d. makes no difference to the shape of the curve. |
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In a filament bulb, what does resistance do?
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It increases with increase of the filment temperature.
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What is the resistance in a diode?
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'forward' resistance is low
'reverse' resistance is high so the current is virtually zero. |
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What is the resistance in a thermistor?
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Resistance decreases if its temperature increases.
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What is the resistance in a light-dependent resistor? (LDR)
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Resistance decreases if the light intensity on it increases.
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For components in series what is the current like, what do you get if you add the potential difference.
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The current is the same in each component
Adding the potential differences gives the total potential difference. |
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What is the total potential difference for cells in series acting in the same direction?
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The sum of their individual potential differences.
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What happens in a series circuit if one compnent stops working?
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The current in the circuit is zero
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The bigger the resistance of a component,
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The bigger its share of the supply potential difference.
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For components in parallel: what is the p.d. like, what is the total current?
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The total current is the sum of the currents through the separate components.
The potential difference is the same across each component |
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The bigger the resistance of a component,
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The smaller the current is
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Whats the equation for current?
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Potential difference / resistance.
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What happens in a parallel circuit if one component stops working?
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No current passes through that component. The current passing through each of the other components is unchanged ( except for the battery as less current passes through it.)
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