Use of electricity to cure mental diseases

1. Listen to the talk about the use of electricity to cure mental diseases, decide whether the statement is true or false.

1. Parkinson's disease causes uncontrollable shaking, or tremors

2. Mr. Dewsnap couldn't use ... the right side of his body.

3. Caleb Kemere has been using brain stimulation in his experiments on frogs.

4. A brain chemical called Dopamine helps control movement.

5. Researchers need to settle some small problems such as what electrical device to use.

2. Listen again and take notes.

3. Describe this method and its difficulties in your own words (in pairs)

Writing (Rendering of the text)

1. Read the text and define the main idea.

2. Make outline and summary of the text.

3. Think about your own ideas on the topic (make use of listening task).

4. Render the text in writing (follow the plan and use expressions – see Appendix)

Feeling electric fields

Why is electricity dangerous to humans? The main reason is that the human body is controlled by ‘electric wires’ itself. As a result, electricity applied to human bodies from the outside interferes with the internal signals. This has been known since 1789. In that year the Italian medical doctor Luigi Galvani (1737–1798) discovered that electrical current makes the muscles of a dead animal contract. The famous first experiment used frog legs: when electricity was applied to them, they twitched violently. Subsequent investigations confirmed that all nerves make use of electrical signals. Using electricity, one can make fresh corpses move, for example. Nerves are the «control wires» of animals. We will explore nerves in more detail below.

Being electrically controlled, all mammals can sense strong electric fields. Humans сan sense fields as low as10kV /m, when hair stands on end. In contrast, several animals can sense much weaker electric (and magnetic) fields. Sharks, for example, can detect fields down to 0.5 μV/m using special sensors, the Ampullae of Lorenzini, which are found around their mouth. Sharks use them to detect the field created by prey moving in water; this allows them to catch their prey even in the dark. The elephantnose fish (Gnathonemus petersii), the salamander and the platypus (Ornithorhyncus anatinus), the famous duck-billed mammal, can also sense electric fields, but achieve only sensitivities of the order of mV/m. Like sharks, they use this ability to detect prey in water which is too muddy to see through. The muscles in living prey generate electric fields. This method is also used by the elephantnose fish. The achieved sensitivity is below 2 mV /m. Certain fish, the so-called weakly-electric fish ,even generate a weak field in order to achieve better prey detection. In fact, several electric fish use time-varying electric dipole fields to communicate! They tell each other their species, their sex, their identity, and communicate about courtship, aggression, appeasement and dangers. The frequencies they use are in the range between a few and 200 Hz, and the fields are dipole fields created between the anterior and posterior sections of their bodies.

No land animal has special sensors for electric fields, because any electric field in air is strongly damped when it encounters a water-filled animal body. Indeed, the usual atmosphere has a low, vertical electric field of around 100 V/m; inside the human body this field is damped to the μV/m range, which is far less than an animal’s internal electric fields. In other words, humans do not have sensors for low electric fields because they are land animals. (Do humans have the ability to sense electric fields in water? Nobody seems to know.) However, there a few exceptions. You might know that some older people can sense approaching thunderstorms in their joints. This is due the coincidence between the electromagnetic field frequency emitted by thunderclouds – around 100 kHz – and the resonant frequency of nerve cell membranes.

The water content of the human body also means that the electric fields in air that are found in nature are rarely dangerous to humans. But whenever humans consciously sense electric fields, such as when high voltage makes their hair stand on end, the situation is potentially dangerous.

The high impedance of air also means that, in the case of time-varying electromagnetic fields, humans are much more prone to be affected by the magnetic component than by the electric component

Can humans feel magnetic fields? So far, there is no definite answer. Magnetic material seems to be present in the human brain, but whether humans can feel magnetic fields is still an open issue. Maybe you can devise a way to check this?

(from Christoph Schiller “MOTION MOUNTAIN”)

Part VI

Listening 2

Lightning and electricity

1. Listen and choose the best answer

1. Benjamin Franklin was…

1. Politician

2. Scientist and inventor

3. All of the above

2. Franklin’s experiment would discover…

1. If lightning would pass through kite

2. If lightning would pass through metal

3. If lightning would strike a tree

3. The kite in the experiment was made….

1. From light metal

2. From brightly colored paper

3. From light cloth

4. The experiment took place in….

1. June, 1752

2. July, 1762

3. January, 1742

5. The experiment proved that lightning is…

1. Sound

2. Light

3. Electricity

6. Fulgurites form when…

1. Lightning strikes sand

2. Lightning strikes rock

3. All of the above

7. Franklin’s invention is…

1. Electricity

2. Metal kite

3. None of the above

2. Explain Franklin’s experiment and its effect

3.Translate from Russian into English

Молния — гигантский электрический искровой разряд в атмосфере, обычно может происходить во время грозы, проявляющийся яркой вспышкой света и сопровождающим её громом. Молнии также были зафиксированы на Венере, Юпитере, Сатурне и Уране и др. Ток в разряде молнии достигает 10—300 тысяч ампер, напряжение — от десятков миллионов до миллиарда вольт. Мощность разряда - от 1 до 1000 ГВт.

Электрическая природа молнии была раскрыта в исследованиях американского физика Б. Франклина, по идее которого был проведён опыт по извлечению электричества из грозового облака. Широко известен опыт Франклина по выяснению электрической природы молнии. В 1750 году им опубликована работа, в которой описан эксперимент с использованием воздушного змея, запущенного в грозу. Опыт Франклина был описан в работе Джозефа Пристли.

Средняя длина молнии 2,5 км, некоторые разряды простираются в атмосфере на расстояние до 20 км.

Удары М. могут сопровождаться разрушениями, вызванными её термическими и электродинамическими воздействиями, а также некоторыми опасными последствиями, возникающими в результате её электромагнитного и светового излучения. Наибольшие разрушения вызывают удары М. в наземные объекты при отсутствии хороших токопроводящих путей между местом удара и землёй. От электрического пробоя в материале образуются узкие каналы, в которые устремляется ток М. Поскольку в каналах создаётся очень высокая температура, часть материала интенсивно испаряется со взрывом. Это приводит к разрыву или расщеплению объекта, пораженного М., и воспламенению его горючих элементов. Наряду с этим возможно возникновение больших разностей потенциалов и электрических разрядов между отдельными предметами внутри строения. Такие разряды могут также явиться причиной пожаров и поражения людей электрическим током.

Speaking

1.Deliver a lecture on Electric current, give all necessary definitions and explain formulas. Use the plan (you may add some points):

1. What is called an electric current?

2. What is resistance?

3. What factors affect electrical resistance?

4. What is resistivity?

5. How can the resistance of a conductor be determined if its length, material and cross-section are known?

6. Define effects.

2. Discussion. Work in pairs or small groups. Compare your answers.

For fun

1. Birds come to no harm when they sit on unprotected electricity lines. Nevertheless, one almost never observes any birds on tall, high voltage lines of 100 kV or more, which transport power across longer distances. Why?

2. Why do we often see shadows of houses and shadows of trees, but never shadows of the electrical cables hanging over streets?

3. A pure magnetic field cannot be transformed into a pure electric field by change of observation frame. The best that can be achieved is a state similar to an equal mixture of magnetic and electric fields. Can you provide an argument elucidating this relation?

4. Five positive charges of magnitude q are arranged symmetrically around the circumference of a circle of radius r. What is the magnitude of the electric field at the center of the circle? (k =1/4πϵ0 )

(A) 0

(B) kq/ r²

(C) 5 kq/ r²

(D) (kq/ r²) cos (2π/ 5)

(E) (5kq/ r²) cos (2π/ 5)

5. A 3-microfarad capacitor is connected in series with a 6-microfarad capacitor. When a 300-volt potential difference is applied across this combination, the total energy stored in the two capacitors is

(A) 0.09 J

(B) 0.18 J

(C) 0.27 J

(D) 0.41 J

(E) 0.81 J

Supplementary reading