16A
YOUR ANSWER:
(A) P = 2.5 watts.
(B) P = 1 watt.
Right you are.
Electrical lamps and soldering irons are examples of electrical devices that are rated in
watts. The wattage rating of a device indicates the rate at which the device converts electrical
energy (power) into another form of energy, such as light and heat.
For example, a 100-watt lamp will produce a brighter light than a 75-watt lamp, because
it converts more electrical energy into light energy.
Electric soldering irons are of various wattage ratings, with the high wattage irons
changing more electrical energy to heat energy that those of low wattage ratings.
Rather than indicate a device's ability to do work, its wattage rating may indicate the
device's operating limit. These power limits generally are given as the maximum or minimum
safe voltages and currents to which a device may be subjected. However, in cases where a
device is not limited to any specific operating voltage, its limits are given directly in watts.
The basic power formula is:
P =E x l.
frame 18A
P= I x R.
frame 10B
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