Презентация (1)

To recall the symbols for different circuit components.
To investigate the characteristics of different components.
Draw and explain the characteristics for a wire, a filament bulb, thermistor and diode.

Explain how and why resistance depends on temperature for metals and semiconductors.

For a resistor, the current-voltage graph is a straight line through the origin.
The current through a resistor is _________ _________to the potential difference (voltage) across the resistor.

Note that for an Ohmic conductor the gradient of the line an I-V graph is equal to 1/R.



But this is for an Ohmic conductor only.
This is because R for a metallic conductor is constant under constant physical conditions.
It does not apply for the filament bulb.

Ohmic or not?

For a filament lamp, as the voltage increases, so does the current.

But the increased current ________the temperature of the filament bulb which also __________the _________.

The curve is _____________

Ohmic, Non Ohmic, Decrease, Increase, Raise Resistance.

At a higher temperature the resistance is _________ than at a lower resistance.

The diode only allows current to flow in one direction (forward direction).

The diode has a _________resistance in the opposite direction (reverse direction).

Needs a certain pd to conduct (typically about 0.6 V for silicon diode.)
High, Low, Don’t know

The graph is Ohmic

A: True
B: False

The resistance is:
A Increasing
B Decreasing
C: Constant
It is impossible to tell from the graph

The resistance of a wire is defined as 2) _______


A) (current)*(voltage). B) (voltage)/(current).
C) (current)/(voltage). D) none of the given answers

2) The resistance of a wire is defined as 2) _______
A) (current)*(voltage). B) (voltage)/(current).
C) (current)/(voltage). D) none of the given answers

When two or more resistors are connected in series to a battery 18) ______
A) the same current flows through each resistor.
B) the equivalent resistance of the combination is equal to the sum of the resistances of each resistor.
C) the total voltage across the combination is the algebraic sum of the voltages across the individual resistors.
D) all of the given answers