Page 11 - 10-phy-14 Current Electricity

No. Resistance Resistance Resistance Sum of Equivalent Observed Differ-
of Reciprocals Resistance Equivalen ence
Obs. resistance Re - R
of Re
R1 = V R2 = V R3 = V resistances V (W)
I1 I2 I3 (W) I¢
DO YOU KNOW? 1 = 1+1+1 R =
Re R1 R2 R3
When a low resistance is
connected in parallel with (W) (W) (W) (W) (W)
a galvanometer, it is called
a shunt. 1

2

3

Table 14.3.2

Conclusions 1.

2.

3.

Post Lab. 1. Resistances of values 1, 100W and 1000 W are connected in parallel.
Activities What is the equivalent resistance of the combination? What conclusion
do you draw from this example?
DO YOU KNOW? 2. ________________________________________________________
3 ________________________________________________________
When current passes
through a resistor, it is An ammeter is formed by shunting a galvanometer with a low resistance.
heated up and sometimes If the resistance of the galvanometer is 50 ohm and that of the shunt is
it also burns up. In order 0.0001 ohms, what is the resistance of the ammeter?
to avoid this mishap, ________________________________________________________
resistors are designed to ________________________________________________________
dissipate power without A current of 2mA is passing through a resistance of 1kΩ (Fig.14.3.2a).
overheating. This power
is indicated by the Voltmeter
wattage of the resistor.
The wattage depends 1mA + V -
upon the size and 1kW
material of the resistor.
1kW Nichrome wire

2mA Resistor 2mA 1mA 1kW 2mA
Fig. 14.3.2(a) Fig. 14.3.2(b)

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