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Resistors
Copy the graph of current – potential for a resistor (figure 3 p. 155) and label it.
Define what an ohmic conductor is, how does resistance vary with the
direction of current?
Answer Qs 1 and 2 p. 155 in full in your book.
More Current-Potential Graphs p. 156-157
Draw how the current and potential difference varies through a filament bulb
(Fig 1). Use the information to describe why the graph is this shape.
Use R = V/I and the graph to answer question a.
Draw how the current and potential difference varies through a diode (Fig 2).
Use the information to describe why the graph is this shape.
Answer question b
Draw how the current and potential difference varies through a Thermistor
and LDR (Figs 4 & 5). Use the information to describe why the graph is this
shape.
Answer Questions c & d
Complete the summary questions on page 157 in full.
LDRS and Thermistors – summary Questions
1. Complete the following using the key words: diode; filament lamp; resistor; and
thermistor
a) The resistance of a... decreases as its temperature increases.
b) The resistance of a… depends on which way round it is connected in a circuit.
c) The resistance of a… increases as the current through it increases.
d) The resistance of a… does not depend on the current through it.
2. A thermistor connected in series with an ammeter and a 3V battery is shown
a) At 15oC the current through the thermistor is 0.2A and the potential difference
across it is 3V – calculate its resistance at this temperature
b) State and explain what happens to the ammeter reading if the thermistor’s
temperature is increased
Answers
1.
a) The resistance of a thermistor decreases as its temperature increases
b) The resistance of a diode depends on which way round it is connected in a circuit
c) The resistance of a filament lamp increases as the current through it increases
d) The resistance of a resistor does not depend on the current through it
2.
a) Resistance = 15Ω (V/I)
b) The ammeter reading increases because the resistance of the thermistor decreases