A current of 200mA through a conductor converts 40 joules of electrical energy into heat in 30 seconds determine the potential drop across the conductor

V = 6.65 [volt]

Explanation:

We must first find the power generated, power is defined as the amount of energy consumed or generated in a given time.

where:

P = power [w]

E = energy = 40 [J]

t = time = 30 [s]

Now we can calculate the voltage or potential drop by means of the power, the power is calculated by means of the product of the voltage by the current.

where:

V = voltage [volts]

I = current = 200mA = 0.2 [A]

Chemists identify substances on the basis of their chemical and physical properties. One

physical property is the amount of energy each gram of a substance will absorb. This property

can be measured quite accurately and is called specific heat (Cp). Specific heat is the amount

of energy, measured in joules, needed to raise the temperature of one gram of the substance

one Celsius degree. Often applied to metallic elements, specific heat can be used as a basis

for comparing how different substances absorb and transfer energy.

To measure specific heat in the laboratory, a calorimeter of some kind must be used. A

calorimeter is a well-insulated container that can measure energy changes. The calorimeter is

insulated to reduce the loss or gain of energy to or from the surroundings. Energy always

flows from an object at a higher temperature to an object at a lower temperature. The heat

gained by the cooler substance equals the heat lost by the warmer substance, if we assume

no loss of heat to the surrounding environment.

heat lost by substance = heat gained by water

In this experiment, you will determine the specific heat of a substance. The substance will

be heated to a high temperature then placed into a calorimeter containing a known quantity of

water at a lower temperature. Having measured the mass of the water in the calorimeter, the

temperature change of the water (T), and knowing the specific heat of water (4.184 J/g -° C),

the heat gained by the water (lost by the substance) can be calculated as follows:

The specific heat of the substance can now be calculated:

Purpose:

In this experiment, you will:

 measure the mass and temperature of water in a calorimeter,

 heat a substance of known mass to a specific temperature,

 calculate the change in water temperature caused by adding the hot substance, and

 calculate the specific heat of the substance using your mass and temperature data.

Materials: goggles and apron hot plate (or burner with tripod stand)

can (or 1000 mL beaker) substances – metal bars

thermometer balance

calorimeter (2 cups with lid) crucible tongs